2024-03-28T14:47:39Zhttps://www.repo.uni-hannover.de/oai/requestoai:www.repo.uni-hannover.de:123456789/222022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Ballistic bipolar junctions in chemically gated graphene ribbons
Baringhaus, Jens
Stöhr, Alexander
Forti, Stiven
Starke, Ulrich
Tegenkamp, Christoph
Surfaces
interfaces and thin films
Graphene
Electronic properties and devices
Graphen
Oberfläche
ddc:530
Graphen
The realization of ballistic graphene pn-junctions is an essential task in order to study Klein tunneling phenomena. Here we show that intercalation of Ge under the buffer layer of pre-structured SiC-samples succeeds to make truly nano-scaled pn-junctions. By means of local tunneling spectroscopy the junction width is found to be as narrow as 5 nm which is a hundred times smaller compared to electrically gated structures. The ballistic transmission across the junction is directly proven by systematic transport measurements with a 4-tip STM. Various npn- and pnp-junctions are studied with respect to the barrier length. The pn-junctions are shown to act as polarizer and analyzer with the second junction becoming transparent in case of a fully ballistic barrier. This can be attributed to the almost full suppression of electron transmission through the junction away from normal incidence.
DFG/SPP/1459
status-type:publishedVersion
London : Nature Publishing Group
2015-04-21
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/4
http://www.repo.uni-hannover.de/handle/123456789/22
http://www.nature.com/srep/2015/150421/srep09955/extref/srep09955-s1.pdf
DOI:http://dx.doi.org/10.1038/srep09955
ISSN:2045-2322
Scientific Reports 5 (2015), Artikelnr. 9955
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/232022-12-02T15:12:32Zcom_123456789_1col_123456789_7ddc:550doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersion
Validation of spectral sky radiance derived from all-sky camera images - a case study
Thosing, Korntip
Schrempf, Michael
Riechelmann, Stefan
Seckmeyer, Gunther
CCD Camera
Luminance Distributions
Field-Measurements
Optical-Properties
Irradiance
Algorithm
Skylight
View
CCD Kamera
Leuchtdichteverteilung
Feldmessung
Optische Eigenschaften
Strahlung
Algorithmus
ddc:550
Leuchtdichte
Himmelsstrahlung
Spectral sky radiance (380–760 nm) is derived from measurements with a hemispherical sky imager (HSI)system. The HSI consists of a commercial compact CCD (charge coupled device) camera equipped with a fish-eye lens and provides hemispherical sky images in three reference bands such as red, green and blue. To obtain the spectral sky radiance from these images, non-linear regression functions for various sky conditions have been derived. The camera-based spectral sky radiance was validated using spectral sky radiance measured with a CCD spectroradiometer. The spectral sky radiance for complete distribution over the hemisphere between both instruments deviates by less than 20% at 500 nm for all sky conditions and for zenith angles less than 80 . The reconstructed spectra of the wavelengths 380–760 nm between both instruments at various directions deviate by less than 20% for all sky conditions.
DFG
status-type:publishedVersion
Göttingen : Copernicus
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/5
http://www.repo.uni-hannover.de/handle/123456789/23
DOI:http://dx.doi.org/10.5194/amt-7-2137-2014
ISSN:1867-1381
ESSN:1867-8548
Atmospheric Measurement Techniques 7 (2014), Nr. 7
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/242022-12-02T15:15:01Zcom_123456789_1col_123456789_7ddc:550doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersion
Improved Synthesis of Global Irradiance with One-Minute Resolution for PV System Simulations
Hofmann, Martin
Riechelmann, Stefan
Crisosto, Christian
Mubarak, Riyad
Seckmeyer, Gunther
Radiation
Classification
Distributions
Temperature
Climate
Algorithm
Probability Density
Photovoltaic
Wahrscheinlichkeitsdichte
Radiation
Strahlung
Globalstrahlung
Klassifizierung
Verteilung
Temperatur
Klima
Algorithmus
Photovoltaik
ddc:550
Dichte <Stochastik>
Globalstrahlung
Verteilung
Temperatur
Klima
Algorithmus
Photovoltaik
High resolution global irradiance time series are needed for accurate simulations of photovoltaic (PV) systems, since the typical volatile PV power output induced by fast irradiance changes cannot be simulated properly with commonly available hourly averages of global irradiance. We present a two-step algorithm that is capable of synthesizing one-minute global irradiance time series based on hourly averaged datasets. The algorithm is initialized by deriving characteristic transition probability matrices (TPM) for different weather conditions (cloudless, broken clouds and overcast) from a large number of high resolution measurements. Once initialized, the algorithm is location-independent and capable of synthesizing one-minute values based on hourly averaged global irradiance of any desired location. The one-minute time series are derived by discrete-time Markov chains based on a TPM that matches the weather condition of the input dataset. One-minute time series generated with the presented algorithm are compared with measured high resolution data and show a better agreement compared to two existing synthesizing algorithms in terms of temporal variability and characteristic frequency distributions of global irradiance and clearness index values. A comparison based on measurements performed in Lindenberg, Germany, and Carpentras, France, shows a reduction of the frequency distribution root mean square errors of more than 60% compared to the two existing synthesizing algorithms.
DFG
status-type:publishedVersion
New York : Hindawi Publishing Corporation
2014-11-26
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/6
http://www.repo.uni-hannover.de/handle/123456789/24
DOI:http://dx.doi.org/ 10.1155/2014/808509
ISSN:1110-662X
ESSN:1687-529X
Journal of Photoenergy 2014 (2014), Artikel-Nr. 808509
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/252022-12-02T15:12:32Zcom_123456789_1col_123456789_7ddc:550doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersion
Comparing satellite- to ground-based automated and manual cloud coverage observations – a case study
Werkmeister, Astrid
Lockhoff, M.
Schrempf, Michael
Tohsing, Korntip
Liley, B.
Seckmeyer, Gunther
AVHRR Data
Clear-Sky
Part I
CM-SAF
Classification
Validation
Imagery
Radiation
Surface
Dynamic Thresholds
Dynamische Schwelle
AVHRR-Daten
klarer Himmel
CM-SAF
Klassifizierung
Validierung
Bild
Radiation
Strahlung
Oberfläche
ddc:550
AVHRR
Strahlung
In this case study we compare cloud fractional cover measured by radiometers on polar satellites (AVHRR) and on one geostationary satellite (SEVIRI) to ground-based manual (SYNOP) and automated observations by a cloud camera (Hemispherical Sky Imager, HSI). These observations took place in Hannover, Germany, and in Lauder, New Zealand, over time frames of 3 and 2 months, respectively. Daily mean comparisons between satellite derivations and the ground-based HSI found the deviation to be 6 14% for AVHRR and 8 16% for SEVIRI, which can be considered satisfactory. AVHRR’s instantaneous differences are smaller (2 22 %) than instantaneous SEVIRI cloud fraction estimates (8 29 %) when compared to HSI due to resolution and scenery effect issues. All spaceborne observations show a very good skill in detecting completely overcast skies (cloud cover 6 oktas) with probabilities between 92 and 94% and false alarm rates between 21 and 29% for AVHRR and SEVIRI in Hannover, Germany. In the case of a clear sky (cloud cover lower than 3 oktas) we find good skill with detection probabilities between 72 and 76 %. We find poor skill, however, whenever broken clouds occur (probability of detection is 32% for AVHRR and 12% for SEVIRI in Hannover, Germany). In order to better understand these discrepancies we analyze the influence of algorithm features on the satellite-based data. We find that the differences between SEVIRI and HSI cloud fractional cover (CFC) decrease (from a bias of 8 to almost 0 %) with decreasing number of spatially averaged pixels and decreasing index which determines the cloud coverage in each “cloud-contaminated” pixel of the binary map. We conclude that window size and index need to be adjusted in order to improve instantaneous SEVIRI and AVHRR estimates. Due to its automated operation and its spatial, temporal and spectral resolution, we recommend as well that more automated ground-based instruments in the form of cloud cameras should be installed as they cover larger areas of the sky than other automated ground-based instruments. These cameras could be an essential supplement to SYNOP observation as they cover the same spectral wavelengths as the human eye.
DFG
status-type:publishedVersion
Göttingen : Copernicus
2015-05-06
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/7
http://www.repo.uni-hannover.de/handle/123456789/25
DOI:http://dx.doi.org/10.5194/amt-8-2001-2015
ISSN:1867-1381
ESSN:1867-8548
Atmospheric Measurement Techniques 8 (2015), Nr. 5, S. 2001-2015
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/402022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Bow-tie nano-antenna assisted generation of extreme ultraviolet radiation
Pfullmann, N.
Waltermann, C.
Noack, M.
Rausch, S.
Nagy, T.
Reinhardt, C.
Kovacev, M.
Knittel, V.
Bratschitsch, R.
Akemeier, D.
Huetten, A.
Leitenstorfer, A.
Morgner, Uwe
laser oscillator
plasmonics
high-harmonic generation
bow-tie antennae
ddc:530
We report on the generation of extreme ultraviolet radiation utilizing the plasmonic field enhancement in arrays of bow-tie gold optical antennae. Furthermore, their suitability to support high-order harmonic generation is examined by means of finite-difference time-domain calculations and experiments. Particular emphasis is paid to the thermal properties, which become significant at the employed peak intensities. A damage threshold depending on the antenna length is predicted and confirmed by our experimental findings. Moreover, the gas density in the vicinity of the antennae is characterized experimentally to determine the number of atoms contributing to the measured radiation, which is almost an order of magnitude larger than previously reported.
DFG/EXC/QUEST
status-type:publishedVersion
Bristol : IOP Publishing Ltd
2013
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/22
http://www.repo.uni-hannover.de/handle/123456789/40
DOI:http://dx.doi.org/10.1088/1367-2630/15/9/093027
ISSN:1367-2630
New Journal of Physics 15 (2013), Nr. 9
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/432022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Origin of metallicity in atomic Ag wires on Si(557)
Krieg, U.
Lichtenstein, T.
Brand, C.
Tegenkamp, Christoph
Pfnür, Herbert
plasmons in one dimension
wire doping
high resolution electron loss spectroscopy
tunelling microscopy
one-dimensional plasmons
plasmon
monolayer
doping
Ag
silicon
Si
surface
Plasmon
eindimensionale Plasmonen
1D-Plasmonen
Monoschicht
Silber
Ag
Si
Silicium
silver
ddc:530
Plasmon
Dimension 1
Monoschicht
Silber
Silicium
Oberfläche
We investigated the metallicity of Ag-root 3 ordered atomic wires close to one monolayer (ML) coverage, which are formed on Si(557) via self assembly. For this purpose we combined high resolution electron energy loss spectroscopy with tunneling microscopy. By extending the excess Ag coverage up to 0.6 ML on samples annealed at high temperatures where partial desorption occurs, we demonstrate that one-dimensional metallicity in the Ag-root 3 x root 3 R30 degrees ordered atomic wires on the (111) mini-terraces originates only from Ag atoms in excess of (local) monolayer coverage, which are adsorbed and localized at the highly stepped parts of the Si(557) surface. Thus these Ag atoms act as extrinsic dopants on the atomic scale, causing coverage dependent subband filling and increasing localization as a function of doping concentration. The second layer lattice gas as well as Ag islands on the (111) terraces turn out not to be relevant as dopants. We simulated the peculiar saturation behavior within a modified lattice gas model and give evidence that the preparation dependent saturation of doping is due to changes of average terrace size and step morphology induced by high temperature treatment.
Niedersächsisches Ministerium für Wissenschaftund Kultur
DFG/FOR/1700
status-type:publishedVersion
Bristol : IOP Publishing Ltd
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/25
http://www.repo.uni-hannover.de/handle/123456789/43
DOI:http://dx.doi.org/10.1088/1367-2630/17/4/043062
ISSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/442022-12-02T15:15:01Zcom_123456789_1col_123456789_7ddc:550doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersion
Second-moment budgets in cloud topped boundary layers: A large-eddy simulation study
Heinze, Rieke
Mironov, Dmitrii
Raasch, Siegfried
large-eddy simulation
cloud topped boundary layers
atmospheric turbulence
modeling
parameterizations
second-moment budgets
LES
boundary layer process
Subgrid-scale parameterization
SGS
large eddy simulation
Grobstruktursimulation
Large Eddy Simulation
LES
Meteorlogie
Atmosphärische Turbulenz
Parametrisierung
Grenzschichtprozess
ddc:550
LES
Atmosphärische Turbulenz
Parametrisierung
Grenzschicht
A detailed analysis of second-order moment budgets for cloud topped boundary layers (CTBLs) is performed using high-resolution large-eddy simulation (LES). Two CTBLs are simulated—one with trade wind shallow cumuli, and the other with nocturnal marine stratocumuli. Approximations to the ensemble-mean budgets of the Reynolds-stress components, of the fluxes of two quasi-conservative scalars, and of the scalar variances and covariance are computed by averaging the LES data over horizontal planes and over several hundred time steps. Importantly, the subgrid scale contributions to the budget terms are accounted for. Analysis of the LES-based second-moment budgets reveals, among other things, a paramount importance of the pressure scrambling terms in the Reynolds-stress and scalar-flux budgets. The pressure-strain correlation tends to evenly redistribute kinetic energy between the components, leading to the growth of horizontal-velocity variances at the expense of the vertical-velocity variance which is produced by buoyancy over most of both CTBLs. The pressure gradient-scalar covariances are the major sink terms in the budgets of scalar fluxes. The third-order transport proves to be of secondary importance in the scalar-flux budgets. However, it plays a key role in maintaining budgets of TKE and of the scalar variances and covariance. Results from the second-moment budget analysis suggest that the accuracy of description of the CTBL structure within the second-order closure framework strongly depends on the fidelity of parameterizations of the pressure scrambling terms in the flux budgets and of the third-order transport terms in the variance budgets.
COST/ES/0905
DFG
status-type:publishedVersion
Hoboken : Wiley Periodicals
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/26
http://www.repo.uni-hannover.de/handle/123456789/44
DOI:http://dx.doi.org/10.1002/2014MS000376
ESSN:1942-2466
Journal of Advances in Modeling Earth Systems 7 (2015), Nr. 2, S. 510-536
eng
CC BY-NC-ND 4.0 Unported
http://creativecommons.org/licenses/by-nc-nd/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/452022-12-02T15:15:01Zcom_123456789_1col_123456789_7ddc:550doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersion
The Parallelized Large-Eddy Simulation Model (PALM) version 4.0 for atmospheric and oceanic flows: model formulation, recent developments, and future perspectives
Maronga, Björn
Gryschka, Micha
Heinze, Rieke
Hoffmann, Fabian
Kanani-Sühring, Farah
Keck, Marius
Ketelsen, K.
Letzel, M.O.
Sühring, Matthias
Raasch, Siegfried
large eddy simulation
large-eddy simulation
LES
PALM
meteorology
Software
Large Eddy Simulation
LES
Turbulente Strömung
Grobstruktursimulation
PALM
Meteorlogie
Software
ddc:550
ddc:551
LES
Meteorlogie
Software
In this paper we present the current version of the Parallelized Large-Eddy Simulation Model (PALM) whose core has been developed at the Institute of Meteorology and Climatology at Leibniz Universität Hannover (Germany). PALM is a Fortran 95-based 5 code with some Fortran 2003 extensions and has been applied for the simulation of a variety of atmospheric and oceanic boundary layers for more than 15 years. PALM is optimized for use on massively parallel computer architectures and was recently ported to general-purpose graphics processing units. In the present paper we give a detailed description of the current version of the model and its features, such as an embedded 10 Lagrangian cloud model and the possibility to use Cartesian topography. Moreover, we discuss recent model developments and future perspectives for LES applications.
DFG/RA/617/3
DFG/RA/617/6
DFG/RA/617/16
DFG/RA/617/27-1
status-type:publishedVersion
Göttingen : Copernicus
2015-02-19
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/27
http://www.repo.uni-hannover.de/handle/123456789/45
http://www.geosci-model-dev-discuss.net/8/1539/2015/gmdd-8-1539-2015-discussion.html
http://palm.muk.uni-hannover.de/
DOI:http://dx.doi.org/10.5194/gmdd-8-1539-2015
ISSN:1991-9611
ESSN:1991-962X
Geoscientific Model Development Discussions 8 (2015), Nr. 2, S. 1539-1637
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/492022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Uncertainty analysis for the coefficient of band-to-band absorption of crystalline silicon
Schinke, Carsten
Peest, Peter Christian
Schmidt, Jan
Brendel, Rolf
Bothe, Karsten
Vogt, Malte R.
Kröger, Ingo
Winter, Stefan
Schirmacher, Alfred
Lim, Siew
Nguyen, Hieu T.
MacDonald, Daniel
crystalline silicon
silicon
absorption coefficient
error analysis
solar cells
photoluminescence
Photovoltaic
kristallines Silizium
c-Si
Silizium
Absorptionskoeffizient
Fehleranalyse
Solarzelle
Photovoltaikzelle
Photolumineszenz
Fotolumineszenz
Photovoltaik
ddc:530
Silicium
Absorptionskoeffizient
Fehleranalyse
Solarzelle
Photolumineszenz
Fotovoltaik
Metallic Zn nanodisks with hexagonal morphology were obtained onto glass substrate under vacuum thermal evaporation. A thermal characterization of Zn nanodiks showed a lower oxidation temperature than source powder Zn. Different thermal treatment on Zn nanodisks played an important role on the morphology, crystal size and surface vibrational modes of ZnO. The growth of ZnO nanoneedles started at the edge of metallic zinc hexagonal structures according with SEM images, the higher temperature the longer needles were grown. XRD diffractogram confirmed the wurtzite structure of ZnO with metallic nuclei. A wide band between 530 and 580 cm(-1) of Raman scattering corresponded at surface vibrational modes not observed at higher temperature.
Deutsche Bundesstiftung Umwelt
DFG
status-type:publishedVersion
Melville : AIP Publishing LLC
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/31
http://www.repo.uni-hannover.de/handle/123456789/49
DOI:http://dx.doi.org/10.1063/1.4923379
ISSN:2158-3226
AIP Advances 5 (2015), Nr. 6
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/522022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Tuning of one-dimensional plasmons by Ag-Doping in Ag-√3-ordered atomic wires
Krieg, U.
Zhang, Yu
Tegenkamp, Christoph
Pfnür, Herbert
one-dimensional plasmons
Ag monolayer
Si vicinal surface
doping
Si
Silicon
vicinal surface
plasmons in one dimension
Plasmon
eindimensionale Plasmonen
1D-Plasmonen
Monoschicht
Ag-Monoschicht
Silber
Ag
Si
Silicium
vicinale Oberfläche
ddc:530
Plasmon
Dimension 1
Monoschicht
Silber
Silicium
Oberfläche
We generated arrays of silver wires with a height of 1 atom and an average width of 11 atoms on the Si(557) surface via self-assembly with local √3 x √3 order, and investigated the 1D plasmon formation in them using a combination of high-resolution electron loss spectroscopy with low-energy electron diffraction. After a series of thermal desorption experiments followed by adding small concentrations of Ag, pure Ag-√3 ordered arrays of nanowires, separated by (113) facets, are intrinsically semi metallic or semiconducting, i.e., the metallicity of the Ag wires seems to be caused by excess atoms added to the (locally) perfectly ordered √3 x √3 layer. The proof has been carried out by post-adsorption of Ag atoms in the range between 0.004 to 0.03 monolayers and the quantitative determination of the frequency dependence of the 1D plasmon due to this excess Ag concentration. As expected for a doping mechanism, there is no minimum excess concentration. The lack of temperature dependence is not compatible with the formation of an adatom gas in the second layer, but suggests extrinsic doping by adatoms bound at the stepped (113) facets. Although strong deviations from a nearly free electron gas are expected in 1D, the Ag concentration dependence of the 1D plasmonic losses is fully compatible with the √ne dependence predicted by this model. Adsorption of traces of residual gas can have a qualitatively similar doping effect.
Niedersächsisches Ministerium für Wissenschaft und Kultur/Contacts in Nanosystems
DFG
status-type:publishedVersion
Bristol : IOP Publishing Ltd
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/34
http://www.repo.uni-hannover.de/handle/123456789/52
DOI:http://dx.doi.org/10.1088/1367-2630/16/4/043007
ISSN:1367-2630
New Journal of Physics 16 (2014), Nr. 4
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/572022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
String order in dipole-blockaded quantum liquids
Weimer, Hendrik
quantum phase transition
dipolar interaction
Rydberg atoms
Quantenphasenübergang
dipolare Wechselwirkung
Rydberg-Atom
Rydberg-Zustand
ddc:530
Quantenphasenübergang
Zwischenmolekulare Kräfte
Wechselwirkung
Atom
Rydberg-Zustand
We study the quantum melting of quasi-one-dimensional lattice models in which the dominant energy scale is given by a repulsive dipolar interaction. By constructing an effective low-energy theory, we show that the melting of crystalline phases can occur into two distinct liquid phases having the same algebraic decay of density–density correlations but showing a different non-local correlation function expressing string order. We present possible experimental realizations using ultracold atoms and molecules, introducing an implementation based on resonantly driven Rydberg atoms that offers additional benefits compared to a weak admixture of the Rydberg state.
status-type:publishedVersion
Bristol : IOP Publishing Ltd
2014-09-25
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/39
http://www.repo.uni-hannover.de/handle/123456789/57
DOI:http://dx.doi.org/10.1088/1367-2630/16/9/093040
ISSN:1367-2630
New Journal of Physics 16 (2014), Nr. 9
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/702022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Ultracold chemistry and its reaction kinetics
Richter, Florian
Becker, Daniel
Bény, Cédric
Schulze, Torben A.
Ospelkaus, Silke
Osborne, Tobias J.
ultracold molecules
entanglement
nonlinear dynamics
ultracold gases
ultrakalte Moleküle
Nichtlineare Dynamik
ultrakalte Gase
ultrakaltes Gas
ddc:530
Ultrakaltes Molekül
Nichtlineare Dynamik
We study the reaction kinetics of chemical processes occurring in the ultracold regime and systematically investigate their dynamics. Quantum entanglement is found to play a key role in driving an ultracold reaction towards a dynamical equilibrium. In case of multiple concurrent reactions Hamiltonian chaos dominates the phase space dynamics in the mean field approximation.
ERC/QFTCMPS
ERC/SIQS
ERC/POLAR
EXC 201 Quantum Engineering and Space-Time Research
status-type:publishedVersion
Bristol : IOP Publishing Ltd
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/52
http://www.repo.uni-hannover.de/handle/123456789/70
DOI:http://dx.doi.org/10.1088/1367-2630/17/5/055005
ISSN:1367-2630
New Journal of Physics 17 (2015), Nr. 5
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/792022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Manipulation of plasmon electron-hole coupling in quasi-free-standing epitaxial graphene layers
Langer, Thomas
Pfnür, Herbert
Tegenkamp, Christoph
Forti, Stiven
Emtsev, Konstantin
Starke, Ulrich
Siliziumkarbid
Oberfläche
Gas
silicon-carbide
surfaces
gas
ddc:530
Siliciumcarbid
Oberfläche
Gas
We have investigated the plasmon dispersion in quasi-free-standing monolayer graphene (QFMLG) and epitaxial monolayer graphene (MLG) layers by means of angle resolved electron energy loss spectroscopy. We have shown that various intrinsic p-and n-doping levels in QFMLG and MLG, respectively, do not lead to different overall slopes of the sheet plasmon dispersion, contrary to theoretical predictions. Only the coupling of the plasmon to single particle interband transitions becomes obvious in the plasmon dispersion by characteristic points of inflections, which coincide with the location of the Fermi level above or below the Dirac point. Further evidence is given by thermal treatment of the QFML graphene layer with gradual desorption of intercalated hydrogen, which shifts the chemical potential toward the Dirac point. From a detailed analysis of the plasmon dispersion, we deduce that the interaction strength between the plasmon and the electron-hole pair excitation is increased by about 30% in QFMLG compared to MLG, which is attributed to a modified dielectric environment of the graphene film.
DFG/Graphene/1459
status-type:publishedVersion
Bristol : IOP Publishing Ltd
2012-10-29
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/61
http://www.repo.uni-hannover.de/handle/123456789/79
DOI:http://dx.doi.org/10.1088/1367-2630/14/10/103045
ISSN:1367-2630
New Journal of Physics 14 (2012)
eng
CC BY-NC-SA 3.0 Unported
http://creativecommons.org/licenses/by-nc-sa/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/802022-12-02T15:15:01Zcom_123456789_1col_123456789_7ddc:550doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersion
Measurements of spectral snow albedo at Neumayer, Antarctica
Wuttke, Sigrid
Seckmeyer, Gunther
König-Langlo, Gert
polar meteorology
radiative process
atmospheric composition
atmospheric structure
transmission of radiation
scattering of radiation
meteorology
atmospheric dynamics
inhomogeneous surface albedo
radiative-transfer
uv irradiance
erythemal irradiance
davis station
sea-ice
ultraviolet
spectroradiometers
eflectance
model
Antarctica
Polarmeteorologie
Strahlungsprozess
Zusammensetzung
Struktur
Atmosphäre
Strahlungsübertragung
Strahlungsstreuung
Meteorologie
Atmosphärische Dynamik
Antarktis
ddc:550
ddc:551
Meteorologie
Zusammensetzung
Struktur
Atmosphäre
Strahlung
Ultraviolett
Albedo
Antarktis
Spectral albedo in high resolution, from 290 to 1050 nm, has been measured at Neumayer, Antarctica, (70 390 S, 8 150 W) during the austral summer 2003/2004. At 500 nm, the spectral albedo nearly reaches unity, with slightly lower values below and above 500 nm. Above 600 nm, the spectral albedo decreases to values between 0.45 and 0.75 at 1000 nm. For one cloudless case an albedo up to 1.01 at 500 nm could be determined. This can be explained by the larger directional component of the snow reflectivity for direct incidence, combined with a slightly mislevelled sensor and the snow surface not being perfectly horizontal. A possible explanation for an observed decline in albedo is an increase in snow grain size. The theoretically predicted increase in albedo with increasing solar zenith angle (SZA) could not be observed. This is explained by the small range of SZA during albedo measurements, combined with the effect of changing snow conditions outweighing the effect of changing SZA. The measured spectral albedo serves as input for radiative transfer models, describing radiation conditions in Antarctica.
status-type:publishedVersion
Göttingen : Copernicus
2006-03-07
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/62
http://www.repo.uni-hannover.de/handle/123456789/80
DOI:http://dx.doi.org/10.5194/angeo-24-7-2006
ISSN:0992-7689
Annales Geophysicae 24 (2006), Nr. 1
Annales Geophysicae 24 (2006), Nr. 1
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/962022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Loop groups in Yang-Mills theory
Popov, Alexander D.
ddc:530
We consider the Yang-Mills equations with a matrix gauge group G on the de Sitter dS4, anti-de Sitter AdS4 and Minkowski R3,1R3,1 spaces. On all these spaces one can introduce a doubly warped metric in the form View the MathML sourceds2=−du2+f2dv2+h2dsH22, where f and h are the functions of u and View the MathML sourcedsH22 is the metric on the two-dimensional hyperbolic space H2H2. We show that in the adiabatic limit, when the metric on H2H2 is scaled down, the Yang–Mills equations become the sigma-model equations describing harmonic maps from a two-dimensional manifold (dS2, AdS2 or R1,1R1,1, respectively) into the based loop group ΩG=C∞(S1,G)/GΩG=C∞(S1,G)/G of smooth maps from the boundary circle S1=∂H2S1=∂H2 of H2H2 into the gauge group G. For compact groups G these harmonic map equations are reduced to equations of geodesics on ΩG, solutions of which yield magnetic-type configurations of Yang–Mills fields. The group ΩG naturally acts on their moduli space.
DFG/LE 838/13
status-type:publishedVersion
Amsterdam : Elsevier
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/78
http://www.repo.uni-hannover.de/handle/123456789/96
DOI:http://dx.doi.org/10.1016/j.physletb.2015.07.041
ISSN:0370-2693
Physics Letters B 748 (2015)
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/972022-12-02T15:19:56Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Curvature-induced resolution of anti-brane singularities
Junghans, Daniel
Schmidt, Daniel
Zagermann, Marco
Flux compactifications; D-branes; Superstring Vacua
ddc:530
We study AdS(7) vacua of massive type IIA string theory compactified on a 3-sphere with H-3 flux and anti-D6-branes. In such backgrounds, the anti-brane backreaction is known to generate a singularity in the H-3 energy density, whose interpretation has not been understood so far. We first consider supersymmetric solutions of this setup and give an analytic proof that the flux singularity is resolved there by a polarization of the anti-D6-branes into a D8-brane, which wraps a finite 2-sphere inside of the compact space. To this end, we compute the potential for a spherical probe D8-brane on top of a background with backreacting anti-D6-branes and show that it has a local maximum at zero radius and a local minimum at a finite radius of the 2-sphere. The polarization is triggered by a term in the potential due to the AdS curvature and does therefore not occur in non-compact setups where the 7d external spacetime is Minkowski. We furthermore find numerical evidence for the existence of non-supersymmetric solutions in our setup. This is supported by the observation that the general solution to the equations of motion has a continuous parameter that is suggestive of a modulus and appears to control supersymmetry breaking. Analyzing the polarization potential for the non-supersymmetric solutions, we find that the flux singularities are resolved there by brane polarization as well.
DFG
status-type:publishedVersion
New York : Springer
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/79
http://www.repo.uni-hannover.de/handle/123456789/97
http://arxiv.org/abs/1402.6040
DOI:10.1007/JHEP10(2014)034
ISSN:1029-8479
Journal of High Energy Physics 2014 (2014), Nr. 10
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/992022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Auxiliary tensor fields for Sp(2, R) self-duality
Ivanov, Evgeny A.
Lechtenfeld, Olaf
Zupnik, Boris M.
Duality in Gauge Field Theories
Global Symmetries
ddc:530
The coset Sp(2, R)/U(1) is parametrized by two real scalar fields. We generalize the formalism of auxiliary tensor (bispinor) fields in U(1) self-dual nonlinear models of abelian gauge fields to the case of Sp(2, R) self-duality. In this new formulation, Sp(2, R) duality of the nonlinear scalar-gauge equations of motion is equivalent to an Sp(2, R) invariance of the auxiliary interaction. We derive this result in two different ways, aiming at its further application to supersymmetric theories. We also consider an extension to interactions with higher derivatives.
RFBR/12-02-00517
RFBR/13-02-90430
RFBR/13-02-91330
DFG/LE 838/12-1
Heisenberg-Landau program
status-type:publishedVersion
New York : Springer
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/81
http://www.repo.uni-hannover.de/handle/123456789/99
http://arxiv.org/abs/1412.5960
DOI:http://dx.doi.org/10.1007/JHEP03(2015)123
ISSN:1029-8479
Journal of High Energy Physics 2015 (2015), Nr. 3
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1002022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Order α′ heterotic domain walls with warped nearly Kähler geometry
Haupt, Alexander S.
Lechtenfeld, Olaf
Musaev, Edvard T.
Flux compactifications
Solitons Monopoles
Instantons
Supergravity Models
ddc:530
We consider (1+3)-dimensional domain wall solutions of heterotic supergravity on a six-dimensional warped nearly Kähler manifold X 6 in the presence of gravitational and gauge instantons of tanh-kink type as constructed in [1]. We include first order α′ corrections to the heterotic supergravity action, which imply a non-trivial Yang-Mills sector and Bianchi identity. We present a variety of solutions, depending on the choice of instantons, for the special case in which the SU(3) structure on X 6 satisfies W1¯¯¯=0. The solutions preserve two real supercharges, which corresponds to N=1/2 supersymmetry from the four-dimensional point of view. Besides serving as a useful framework for collecting existing solutions, the formulation in terms of dynamic SU(3) structures utilized here allows us to obtain new solutions in as yet unexplored corners of the instanton configuration space. Our approach thus offers a unified description of the embedding of tanh-kink-type instantons into half-BPS solutions of heterotic supergravity where the internal six-dimensional manifold has a warped nearly Kähler geometry.
status-type:publishedVersion
New York : Springer
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/82
http://www.repo.uni-hannover.de/handle/123456789/100
http://arxiv.org/abs/1409.0548
http://arxiv.org/abs/1409.0548v2
DOI:http://dx.doi.org/10.1007/JHEP11(2014)152
ISSN:1029-8479
Journal of High Energy Physics 2014 (2014), Nr. 11
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1012022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
The structure of invariants in conformal mechanics
Hakobyan, Tigran
Karakhanyan, David
Lechtenfeld, Olaf
calogero-moser system
n-body problems
integrable systems
lie-algebras
hamiltonian systems
quantum-mechanics
sutherland model
one-dimension
black-holes
superintegrability
ddc:530
We investigate the integrals of motion of general conformal mechanical systems with and without confining harmonic potential as well as of the related angular subsystems, by employing the sl(2,R) algebra and its representations. In particular, via the tensor product of two representations we construct new integrals of motion from old ones, both in the classical and in the quantum case. Furthermore, the temporally periodic observables (including the integrals) of the angular subsystem are explicitly related to those of the full system in a confining harmonic potential. The techniques are illustrated for the rational Calogero models and their angular subsystems, where they generalize known methods for obtaining conserved charges beyond the Liouville ones.
VolkswagenStiftung/86 260
Arme-nian State Committee of Science/13RF-018
Armenian State Committee of Science/13-1C114
Armenian State Committee of Science/13-1C132
ANSEF/3501
ANSEF/3122
status-type:publishedVersion
Amsterdam : Elsevier Science BV
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/83
http://www.repo.uni-hannover.de/handle/123456789/101
DOI:http://dx.doi.org/10.1016/j.nuclphysb.2014.07.008
ISSN:0550-3213
Nuclear Physics B 886 (2014)
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1022022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Topological invariants and fibration structure of complete intersection Calabi-Yau four-folds
Gray, James
Haupt, Alexander S.
Lukas, Andre
F-Theory
Differential
Algebraic Geometry
Superstring Vacua
ddc:530
We investigate the mathematical properties of the class of Calabi-Yau four-folds recently found in ref. [1]. This class consists of 921,497 configuration matrices which correspond to manifolds that are described as complete intersections in products of projective spaces. For each manifold in the list, we compute the full Hodge diamond as well as additional topological invariants such as Chern classes and intersection numbers. Using this data, we conclude that there are at least 36,779 topologically distinct manifolds in our list. We also study the fibration structure of these manifolds and find that 99.95 percent can be described as elliptic fibrations. In total, we find 50,114,908 elliptic fibrations, demonstrating the multitude of ways in which many manifolds are fibered. A sub-class of 26,088,498 fibrations satisfy necessary conditions for admitting sections. The complete data set can be downloaded here.
SCOAP3
status-type:publishedVersion
New York : Springer
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/84
http://www.repo.uni-hannover.de/handle/123456789/102
http://arxiv.org/abs/1405.2073
http://arxiv.org/abs/1405.2073v2
DOI:http://dx.doi.org/10.1007/JHEP09(2014)093
ISSN:1029-8479
Journal of High Energy Physics 2014 (2014), Nr. 9
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1032022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Quantum corrections in string compactifications on SU(3) structure geometries
Graña, Mariana
Louis, Jan
Theis, Ulrich
Waldram, Daniel
Supersymmetric Effective Theories
Flux compactifications
Superstring Vacua
ddc:530
We investigate quantum corrections to the classical four-dimensional low-energy effective action of type II string theory compactified on SU(3) structure geometries. Various methods previously developed for Calabi-Yau compactifications are adopted to constrain - under some simple assumptions about the low-energy degrees of freedom - the leading perturbative corrections to the moduli space metrics in both α′ and the string coupling constant. We find that they can be parametrized by a moduli dependent function in the hypermultiplet sector and a constant in the vector multiplet sector. We argue that under specific additional assumption they take - in complete analogy to the Calabi-Yau case - a universal form which depends only on the Euler characteristic of the six-dimensional compact space.
SCOAP3
status-type:publishedVersion
New York : Springer
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/85
http://www.repo.uni-hannover.de/handle/123456789/103
http://arxiv.org/abs/1406.0958
http://arxiv.org/abs/1406.0958v2
DOI:http://dx.doi.org/10.1007/JHEP01(2015)057
ISSN:1029-8479
Journal of High Energy Physics 2015 (2015), Nr. 1
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1042022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
The staggered six-vertex model: Conformal invariance and corrections to scaling
Frahm, Holger
Seel, Alexander
lattice potts-model
sl(2,r) wzw model
operator content
heisenberg chain
superspin chain
continuum-limit
quantum chains
critical-point
central charge
field-theory
ddc:530
We study the emergence of non-compact degrees of freedom in the low energy effective theory for a class of Z2Z2-staggered six-vertex models. In the finite size spectrum of the vertex model this shows up through the appearance of a continuum of critical exponents. To analyze this part of the spectrum we derive a set of coupled nonlinear integral equations from the Bethe ansatz solution of the vertex model which allow to compute the energies of the system for a range of anisotropies and of the staggering parameter. The critical theory is found to be independent of the staggering. Its spectrum and density of states coincide with the SL(2,R)/U(1)SL(2,R)/U(1) Euclidean black hole conformal field theory which has been identified previously in the continuum limit of the vertex model for a particular ‘self-dual’ choice of the staggering. We also study the asymptotic behavior of subleading corrections to the finite size scaling and discuss our findings in the context of the conformal field theory.
DFG
status-type:publishedVersion
Amsterdam : Elsevier Science BV
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/86
http://www.repo.uni-hannover.de/handle/123456789/104
DOI:http://dx.doi.org/10.1016/j.nuclphysb.2013.12.015
ISSN:0550-3213
Nuclear Physics B 879 (2014)
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1052022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Finite-size effects in the spectrum of the OSp(3|2) superspin chain
Frahm, Holger
Martins, Márcio J.
staggered 6-vertex model
conformal-invariance
continuum-limit
2 dimensions
lattice-gas
spin chain
point
ddc:530
The low energy spectrum of a spin chain with OSp(3|2)supergroup symmetry is studied based on the Bethe ansatz solution of the related vertex model. This model is a lattice realization of intersecting loops in two dimensions with loop fugacity z=1which provides a framework to study the critical properties of the unusual low temperature Goldstone phase of the O(N)sigma model for N=1in the context of an integrable model. Our finite-size analysis provides strong evidence for the existence of continua of scaling dimensions, the lowest of them starting at the ground state. Based on our data we conjecture that the so-called watermelon correlation functions decay logarithmically with exponents related to the quadratic Casimir operator of OSp(3|2). The presence of a continuous spectrum is not affected by a change to the boundary conditions although the density of states in the continua appears to be modified.
DFG
FAPESP
CNPq
status-type:publishedVersion
Amsterdam : Elsevier Science BV
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/87
http://www.repo.uni-hannover.de/handle/123456789/105
DOI:http://dx.doi.org/10.1016/j.nuclphysb.2015.03.021
ISSN:0550-3213
Nuclear Physics B 894 (2015)
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1062022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Inversion identities for inhomogeneous face models
Frahm, Holger
Karaiskos, Nikos
nondiagonal boundary terms
8-vertex sos model
xxz spin chain
bethe-ansatz
functional relations
reflection equation
field-theory
representation
ddc:530
We derive exact inversion identities satisfied by the transfer matrix of inhomogeneous interaction-round-a-face (IRF) models with arbitrary boundary conditions using the underlying integrable structure and crossing properties of the local Boltzmann weights. For the critical restricted solid-on-solid (RSOS) models these identities together with some information on the analytical properties of the transfer matrix deter-mine the spectrum completely and allow to derive the Bethe equations for both periodic and general open boundary conditions.
SCOAP3
status-type:publishedVersion
Amsterdam : Elsevier Science BV
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/88
http://www.repo.uni-hannover.de/handle/123456789/106
DOI:http://dx.doi.org/10.1016/j.nuclphysb.2014.08.013
ISSN:0550-3213
Nuclear Physics B 887 (2014)
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1072022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Integrable anyon chains: From fusion rules to face models to effective field theories
Finch, Peter E.
Flohr, Michael
Frahm, Holger
condensed matter
strongly correlated electrons
high energy physics
theory
mathematical physics
conformal invariance
dynkin diagrams
lattice models
spin chain
w-algebras
q-operator
sos model
thermodynamics
construction
excitations
ddc:530
Starting from the fusion rules for the algebra SO(5)2we construct one-dimensional lattice models of interacting anyons with commuting transfer matrices of ‘interactions round the face’ (IRF) type. The con-served topological charges of the anyon chain are recovered from the transfer matrices in the limit of large spectral parameter. The properties of the models in the thermodynamic limit and the low energy excitations are studied using Bethe ansatz methods. Two of the anyon models are critical at zero temperature. From the analysis of the finite size spectrum we find that they are effectively described by rational conformal field theories invariant under extensions of the Virasoro algebra, namely WB2and WD5, respectively. The latter contains primaries with half and quarter spin. The modular partition function and fusion rules are derived and found to be consistent with the results for the lattice model.
SCOAP3
DFG/Fr/737/7
status-type:publishedVersion
Amsterdam : Elsevier Science BV
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/89
http://www.repo.uni-hannover.de/handle/123456789/107
http://arxiv.org/abs/1408.1282
DOI:http://dx.doi.org/10.1016/j.nuclphysb.2014.10.017
ISSN:0550-3213
Nuclear Physics B 889 (2014)
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1082022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Sigma-model limit of Yang–Mills instantons in higher dimensions
Deser, Andreas
Lechtenfeld, Olaf
Popov, Alexander D.
high energy physics
theory
mathematical physics
mathematics
differential geometry
stable vector-bundles
chern-simons theory
greater-than 4
gauge-theory
calibrated geometry
holonomy manifolds
fields
equations
connections
reduction
ddc:530
We consider the Hermitian Yang–Mills (instanton) equations for connections on vector bundles over a 2n-dimensional Kähler manifold Xwhich is a product Y×Zof p-and q-dimensional Riemannian manifold Yand Zwith p+q=2n. We show that in the adiabatic limit, when the metric in the Zdirection is scaled down, the gauge instanton equations on Y×Zbecome sigma-model instanton equations for maps from Yto the moduli space M(target space) of gauge instantons on Zif q≥4. For q<4we get maps from Yto the moduli space Mof flat connections on Z. Thus, the Yang–Mills instantons on Y×Zconverge to sigma-model instantons on Ywhile Zshrinks to a point. Put differently, for small volume of Z, sigma-model instantons on Ywith target space Mapproximate Yang–Mills instantons on Y×Z.
DFG/LE/838/13
status-type:publishedVersion
Amsterdam : Elsevier Science BV
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/90
http://www.repo.uni-hannover.de/handle/123456789/108
http://arxiv.org/abs/1412.4258
http://arxiv.org/abs/1412.4258v3
DOI:http://dx.doi.org/10.1016/j.nuclphysb.2015.03.009
ISSN:0550-3213
Nuclear Physics B 894 (2015)
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1092022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Nonlinear supersymmetry in the quantum Calogero model
Correa, Francisco
Lechtenfeld, Olaf
Plyushchay, Mikhail
Integrable Equations
Conformal Symmetry
W Symmetry
Extended Supersymmetry
ddc:530
It is long known that the rational Calogero model describing n identical particles on a line with inverse-square mutual interaction potential is quantum superintegrable. We review the (nonlinear) algebra of the conserved quantum charges and the intertwiners which relate the Liouville charges at couplings g and g±1. For integer values of g, these intertwiners give rise to additional conserved charges commuting with all Liouville charges and known since the 1990s. We give a direct construction of such a charge, the unique one being totally antisymmetric under particle permutations. It is of order 12 n(n−1)(2g−1) in the momenta and squares to a polynomial in the Liouville charges. With a natural Z 2 grading, this charge extends the algebra of conserved charges to a nonlinear supersymmetric one. We provide explicit expressions for intertwiners, charges and their algebra in the cases of two, three and four particles.
SCOAP3
status-type:publishedVersion
New York : Springer
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/91
http://www.repo.uni-hannover.de/handle/123456789/109
http://arxiv.org/abs/1312.5749
http://arxiv.org/abs/1312.5749v2
DOI:http://dx.doi.org/10.1007/JHEP04(2014)151
ISSN:1029-8479
Journal of High Energy Physics 2014 (2014), Nr. 4
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1112022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Dirac structures on nilmanifolds and coexistence of fluxes
Chatzistavrakidis, Athanasios
Jonke, Larisa
Lechtenfeld, Olaf
high energy physics
theory
mathematical physics
poisson manifolds
lie bialgebroids
string theory
compactifications
tori
ddc:530
We study some aspects of the generalized geometry of nilmanifolds and examine to which extent different types of fluxes can coexist on them. Nilmanifolds constitute a class of homogeneous spaces which are interesting in string compactifications with fluxes since they carry geometric flux by construction. They are generalized Calabi–Yau spaces and therefore simple examples of generalized geometry at work. We identify and classify Dirac structures on nilmanifolds, which are maximally isotropic subbundles closed under the Courant bracket. In the presence of non-vanishing fluxes, these structures are twisted and closed under appropriate extensions of the Courant bracket. Twisted Dirac structures on a nilmanifold may carry multiple coexistent fluxes of any type. We also show how dual Dirac structures combine to Courant algebroids and work out an explicit example where all types of generalized fluxes coexist. These results may be useful in the context of general flux compactifications in string theory.
DFG/LE/838/13
status-type:publishedVersion
Amsterdam : Elsevier Science BV
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/93
http://www.repo.uni-hannover.de/handle/123456789/111
http://arxiv.org/abs/1311.4878
http://arxiv.org/abs/1311.4878v2
DOI:http://dx.doi.org/10.1016/j.nuclphysb.2014.03.013
ISSN:0550-3213
Nuclear Physics B 883 (2014)
eng
CC BY 3.0 Unported
http://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1122022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Instantons on conical half-flat 6-manifolds
Bunk, Severin
Lechtenfeld, Olaf
Popov, Alexander D.
Sperling, Marcus
Solitons Monopoles
Instantons
Flux compactifications
Differential Geometry
Algebraic Geometry
ddc:530
We present a general procedure to construct 6-dimensional manifolds with SU(3)-structure from SU(2)-structure 5-manifolds. We thereby obtain half-flat cylinders and sine-cones over 5-manifolds with Sasaki-Einstein SU(2)-structure. They are nearly Kähler in the special case of sine-cones over Sasaki-Einstein 5-manifolds. Both half-flat and nearly Kähler 6-manifolds are prominent in flux compactifications of string theory. Subsequently, we investigate instanton equations for connections on vector bundles over these half-flat manifolds. A suitable ansatz for gauge fields on these 6-manifolds reduces the instanton equation to a set of matrix equations. We finally present some of its solutions and discuss the instanton configurations obtained this way.
DFG/LE/838/13
status-type:publishedVersion
New York : Springer
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/94
http://www.repo.uni-hannover.de/handle/123456789/112
http://arxiv.org/abs/1409.0030
http://arxiv.org/abs/1409.0030v2
DOI:http://dx.doi.org/10.1007/JHEP01(2015)030
ISSN:1029-8479
Journal of High Energy Physics 2015 (2015), Nr.1
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1132022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
On hvLif-like solutions in gauged Supergravity
Bueno, P.
Chemissany, W.
Shahbazi, C.S
Gauge Coupling Constant
Hamiltonian Constraint
Scalar Field
Hyperscaling Violation
Attractor Point
Extremal Black Hole
Cosmological Constant
Dyonic Solution
Flat Direction
Coupling Function
Dilaton Field
Energy-momentum Tensor
Gravity Theory
Negative Cosmological Constant
black-holes
hyperscaling violation
supergravity
ddc:530
We perform a thorough investigation of Lifshitz-like metrics with hyperscaling violation (hvLif) in four-dimensional theories of gravity coupled to an arbitrary number of scalars and vector fields, obtaining new solutions, electric, magnetic, and dyonic, that include the known ones as particular cases. After establishing some general results on the properties of purely hvLif solutions, we apply the previous formalism to the case of N=2, d=4 supergravity in the presence of Fayet–Iliopoulos terms, obtaining particular solutions to the t3-model, and explicitly embedding some of them in Type-IIB string theory.
Spanish Ministry of Science and Education/FPA/2009-07692
Comunidad de Madrid/HEPHACOS S2009ESP-1473
Spanish Consolider-Ingenio 2010 program/CPAN CSD2007-00042
status-type:publishedVersion
New York : Springer
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/95
http://www.repo.uni-hannover.de/handle/123456789/113
DOI:http://dx.doi.org/10.1140/epjc/s10052-013-2684-3
ISSN:1434-6044
The European Physical Journal C 74 (2014), Nr. 1
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1142022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersionddc:510
Discrete R-symmetries and anomaly universality in heterotic orbifolds
Bizet, Nana G. Cabo
Kobayashi, Tatsuo
Peña, Damián K. Mayorga
Parameswaran, Susha L.
Schmitz, Matthias
Zavala, Ivonne
Wilson Line
Orbifold Model
Low Energy Effective Field Theory
Geometrical Symmetry
String Theory
Finite Symmetry
Explicit Computation
Heterotic String
Superstrings
Conformal Field Model
ddc:530
ddc:510
We study discrete R-symmetries, which appear in the 4D low energy effective field theory derived from heterotic orbifold models. We derive the R-symmetries directly from the geometrical symmetries of the orbifolds. In particular, we obtain the corresponding R-charges by requiring that the couplings be invariant under these symmetries. This allows for a more general treatment than the explicit computations of correlation functions made previously by the authors, including models with discrete Wilson lines, and orbifold symmetries beyond plane-by-plane rotational invariance. The R-charges obtained in this manner differ from those derived in earlier explicit computations. We study the anomalies associated with these R-symmetries, and comment on the results.
status-type:publishedVersion
New York : Springer
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/96
http://www.repo.uni-hannover.de/handle/123456789/114
http://arxiv.org/abs/1308.5669
http://arxiv.org/abs/1308.5669v2
DOI:http://dx.doi.org/10.1007/JHEP02(2014)098
ISSN:1029-8479
Journal of High Energy Physics 2014 (2014), Nr. 2
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1152022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Wilson lines and Chern-Simons flux in explicit heterotic Calabi-Yau compactifications
Apruzzi, Fabio
Gautason, Fridrik Freyr
Parameswaran, Susha L.
Zagermann, Marco
Wilson Line
Complete Intersection
Special Lagrangian Submanifolds
Modulo Stabilization
Supersymmetry Breaking Scale
Chern-Simons Term
Calabi-Yau Compactifications
String Model
Large Classis
Heterotic Compactifications
Flux Compactifications
Heterotic Strings
Superstrings
Superstring Vacua
ddc:530
We study to what extent Wilson lines in heterotic Calabi-Yau compactifications lead to non-trivial H-flux via Chern-Simons terms. Wilson lines are basic ingredients for Standard Model constructions but their induced H-flux may affect the consistency of the leading order background geometry and of the two-dimensional worldsheet theory. Moreover H-flux in heterotic compactifications would play an important role for moduli stabilization and could strongly constrain the supersymmetry breaking scale. We show how to compute H-flux and the corresponding superpotential, given an explicit complete intersection Calabi-Yau compactification and choice of Wilson lines. We do so by identifying large classes of special Lagrangian submanifolds in the Calabi-Yau, understanding how the Wilson lines project onto these submanifolds, and computing their Chern-Simons invariants. We illustrate our procedure with the quintic hypersurface as well as the split-bicubic, which can provide a potentially realistic three generation model.
status-type:publishedVersion
New York : Springer
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/97
http://www.repo.uni-hannover.de/handle/123456789/115
http://arxiv.org/abs/1410.2603
http://arxiv.org/abs/1410.2603v2
DOI:http://dx.doi.org/10.1007/JHEP02(2015)183
ISSN:1029-8479
Journal of High Energy Physics 2015 (2015), Nr. 2
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1182022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
AdS6 solutions of type II supergravity
Apruzzi, Fabio
Fazzi, Marco
Passias, Achilleas
Rosa, Dario
Tomasiello, Alessandro
Flux Compactifications
AdS-CFT Correspondence
Pure Spinor
Near-horizon Limit
Massive IIA
Supersymmetric Solution
IIB Supergravity
Eleven-dimensional Supergravity
Two-dimensional Space
ddc:530
Very few AdS6 × M 4 supersymmetric solutions are known: one in massive IIA, and two IIB solutions dual to it. The IIA solution is known to be unique; in this paper, we use the pure spinor approach to give a classification for IIB supergravity. We reduce the problem to two PDEs on a two-dimensional space Σ. M 4 is then a fibration of S 2 over Σ; the metric and fluxes are completely determined in terms of the solution to the PDEs. The results seem likely to accommodate near-horizon limits of (p, q)-fivebrane webs studied in the literature as a source of CFT5’s. We also show that there are no AdS6 solutions in eleven-dimensional supergravity.
status-type:publishedVersion
New York : Springer
2014
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/100
http://www.repo.uni-hannover.de/handle/123456789/118
http://arxiv.org/abs/1406.0852
http://arxiv.org/abs/1406.0852v3
DOI:http://dx.doi.org/10.1007/JHEP11(2014)099
ISSN:1029-8479
Journal of High Energy Physics 2014 (2014), Nr. 11
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/1672022-12-02T16:17:36Zcom_123456789_1col_123456789_7doc-type:Textopen_accessddc:530status-type:publishedVersiondoc-type:DoctoralThesis
Phononenspektroskopie im Quanten-Hall-Effekt-Regime
Schulze Wischeler, Fritz
Haug, Rolf J.
Zeitler, U.
quantum Hall effect
phonons
composite fermion
Quanten-Hall-Effekt
Phononen
Composite Fermion
ddc:530
Quanten-Hall-Effekt
Fraktionierter Quanten-Hall-Effekt
Phonon
Phononenspektroskopie
Composite fermion
Hochschulschrift
In dieser Arbeit wurde der Quanten-Hall-Effekt mit Hilfe von Phononen untersucht. Ziel der Arbeit war es, die thermodynamischen Eigenschaften von zweidimensionalen Elektronensystemen und Größe der Energielücken im fraktionalen Quanten-Hall-Effekt präzise zu vermessen. So gelang es, die Composite-Fermion-Masse und Landé g-Faktoren zu bestimmen. Darüberhinaus konnte die spezifische Wärme eines zweidimensionalen Elektronensystemens für diverse Füllfaktoren gemessen werden, einer thermodynamischen Größe, für die bisher keine experimentelle Technik zur Verfügung stand.
status-type:publishedVersion
Hannover : Technische Informationsbibliothek u. Universitätsbibliothek
2004
doc-type:DoctoralThesis
doc-type:Text
http://dx.doi.org/10.15488/149
http://www.repo.uni-hannover.de/handle/123456789/167
http://nbn-resolving.de/urn:nbn:de:gbv:089-4733931230
ger
CC BY 3.0 DE
http://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/2252022-12-13T15:12:26Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:510
Well-posedness, blow-up phenomena, and global solutions for the b-equation
Escher, Joachim
Yin, Zhaoyang
degasperis-procesi equation
shallow-water equation
camassa-holm equation
korteweg-de-vries
integrable equation
peakon solutions
weak solutions
cauchy-problem
wave solutions
shock-waves
ddc:510
In the paper we first establish the local well-posedness for a family of nonlinear dispersive equations, the so called b-equation. Then we describe the precise blow-up scenario. Moreover, we prove that for the b-equation we do have the coexistence of global in time solutions and blow-up phenomena: Depending on the initial data solutions may exist for ever, while other data force the solution to produce a singularity in finite time. Finally, we prove the uniqueness and existence of global weak solution to the equation provided the initial data satisfy certain sign conditions.
Alexander von Humboldt Foundation
NNSF of China/10531040
NSF of Guangdong Province
SRF for ROCS
status-type:publishedVersion
Berlin : Walter de Gruyter
2008-10-29
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/203
http://www.repo.uni-hannover.de/handle/123456789/225
DOI:http://dx.doi.org/10.1515/CRELLE.2008.080
ISSN:0075-4102
ESSN:1435-5345
Journal für die reine und angewandte Mathematik 2008 (2008), Nr. 624
eng
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/2262022-12-13T15:12:26Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:510
A K-theoretic proof of Boutet de Monvel's index theorem for boundary value problems
Melo, Severino T.
Schick, Thomas
Schrohe, Elmar
algebra
operators
calculus
ddc:510
We study the C*-closure U of the algebra of all operators of order and class zero in Boutet de Monvel's calculus on a compact connected manifold X with boundary partial derivative X not equal phi. We find short exact sequences in K-theory 0 -> K-i (C(X)) -> K-i(U/R) ->(P) K1-i(C-0(T*X degrees)) -> 0, i = 0,1, which split, so that K-i(U/R) congruent to K-i(C(X)) circle plus K1-i(Co(T*X degrees)). Using only simple K-theoretic arguments and the Atiyah-Singer index theorem, we show that the Fredhohn index of an elliptic element in A is given by ind A = ind(t)(p[A])), where [A] is the class of A in K-1(U/R) and ind(t) is the topological index, a relation first established by Boutet de Monvel by different methods.
CNPq/452780/2003-9
CNPq/306214/2003-2
European Research and Training Network ‘‘Geometric Analysis’/HPRN-CT-1999-0018
status-type:publishedVersion
Berlin : Walter de Gruyter
2006-12-07
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/204
http://www.repo.uni-hannover.de/handle/123456789/226
DOI:http://dx.doi.org/10.1515/CRELLE.2006.083
ISSN:0075-4102
ESSN:1435-5345
Journal für die reine und angewandte Mathematik 2006 (2006), Nr. 599
eng
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/2282022-12-13T15:12:26Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:510
Analytic solutions for a Stefan problem with Gibbs-Thomson correction
Escher, Joachim
Pruss, Jan
Simonett, Gieri
phase-transition problems
free-boundary
parabolic equations
classical-solutions
space variables
weak solutions
continuity
regularity
temperature
operators
ddc:510
We provide existence of a unique smooth solution for a class of one- and two-phase Stefan problems with Gibbs-Thomson correction in arbitrary space dimensions. In addition, it is shown that the moving interface depends analytically on the temporal and spatial variables. Of crucial importance for the analysis is the property of maximal L-p-regularity for the linearized problem, which is fully developed in this paper as well.
status-type:publishedVersion
Berlin : Walter de Gruyter
2003
doc-type:Article
doc-type:Text
http://www.repo.uni-hannover.de/handle/123456789/228
https://doi.org/10.15488/206
DOI:http://dx.doi.org/10.1515/crll.2003.082
ISSN:0075-4102
ESSN:1435-5345
Journal für die reine und angewandte Mathematik 2003 (2003), Nr. 563
eng
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/2302022-12-13T15:12:26Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:510
Degenerations of Prym varieties
Alexeev, V.
Birkenhake, C.
Hulek, Klaus
Prym variety
algebra
applied mathematics
ddc:510
Algebra
Angewandte Mathematik
Prym-Varietät
Let (C, l) be a stable curve with an involution. Following a classical construction one can define its Prym variety P, which in this case turns out to be a semiabelian group variety and usually not complete. In this paper we study the question whether there are "good" compactifications of P in analogy to compactified Jacobians. The answer to this question depends on whether we consider degenerations of principally polarized Prym varieties or degenerations with the induced (non-principal) polarization. We describe degeneration data of such degenerations. The main application of our theory lies in the case of degenerations of principally polarized Prym varieties where we ask whether such a degeneration depends on a given one-parameter family containing (C, l) or not. This allows us to determine the indeterminacy locus of the Prym map.
status-type:publishedVersion
Berlin : Walter de Gruyter
2002
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/208
http://www.repo.uni-hannover.de/handle/123456789/230
DOI:http://dx.doi.org/10.1515/crll.2002.103
ISSN:0075-4102
ESSN:1435-5345
Journal für die reine und angewandte Mathematik 2002 (2002), Nr. 553
eng
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/2382022-12-13T15:12:26Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:510
The modularity of the Barth-Nieto quintic and its relatives
Hulek, Klaus
Spandaw, J.
van Geemen, B.
van Straten, D.
Calabi-Yau
algebra
applied mathematis
ddc:510
Calabi-Yau-Mannigfaltigkeit
Algebra
Angewandte Mathematik
The moduli space of (1, 3)-polarized abelian surfaces with full level-2 structure is birational to a double cover of the Barth Nieto quintic. Barth and Nieto have shown that these varieties have Calabi-Yau models Z and Y, respectively. In this paper we apply the Weil conjectures to show that Y and Z are rigid and we prove that the L-function of their common third e A tale cohomology group is modular, as predicted by a conjecture of Fontaine and Mazur. The corresponding modular form is the unique normalized cusp form of weight 4 for the group Gamma(1)(6). By Tate's conjecture, this should imply that Y, the fibred square of the universal elliptic curve S-1(6), and Verrill's rigid Calabi-Yau ZA(3), which all have the same L-function, are in correspondence over Q. We show that this is indeed the case by giving explicit maps.
status-type:publishedVersion
Berlin : Walter de Gruyter
2001-08
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/216
http://www.repo.uni-hannover.de/handle/123456789/238
DOI:http://dx.doi.org/10.1515/advg.2001.017
ISSN:1615-715X
ESSN:1615-7168
Advances in Geometry 1 (2001), Nr. 3
eng
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/2572022-12-13T15:12:26Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:510
On positive solutions of some system of reaction-diffusion equations with nonlocal initial conditions
Walker, Christoph
lotka competition model
differential-equations
population-dynamics
steady-states
predator-prey
bifurcation
pairs
ddc:510
The paper focuses on positive solutions to a coupled system of parabolic equations with nonlocal initial conditions. Such equations arise as steady-state equations in an age-structured predator-prey model with diffusion. By using global bifurcation techniques, we describe the structure of the set of positive solutions with respect to two parameters measuring the intensities of the fertility of the species. In particular, we establish co-existence steady-states, i.e. solutions which are nonnegative and nontrivial in both components.
status-type:publishedVersion
Berlin : Walter de Gruyter
2011-11
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/235
http://www.repo.uni-hannover.de/handle/123456789/257
DOI:http://dx.doi.org/10.1515/CRELLE.2011.074
ISSN:0075-4102
ESSN:1435-5345
Journal für die reine und angewandte Mathematik 2011 (2011), Nr. 660
eng
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/2582022-12-13T15:12:26Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:510
Seminormal forms and Gram determinants for cellular algebras
Mathas, Andrew
Soriano, Marcos
algebra
Cayley-Hamilton theorem
ddc:510
This paper develops an abstract framework for constructing ‘‘seminormal forms’’ for cellular algebras. That is, given a cellular R-algebra A which is equipped with a family of JM-elements we give a general technique for constructing orthogonal bases for A, and for all of its irreducible representations, when the JM-elements separate A. The seminormal forms for A are defined over the field of fractions of R. Significantly, we show that the Gram determinant of each irreducible A-module is equal to a product of certain structure constants coming from the seminormal basis of A. In the non-separated case we use our seminormal forms to give an explicit basis for a block decomposition of A.
status-type:publishedVersion
Berlin : Walter de Gruyter
2008-06
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/236
http://www.repo.uni-hannover.de/handle/123456789/258
DOI:http://dx.doi.org/10.1515/CRELLE.2008.042
ISSN:0075-4102
ESSN:1435-5345
Journal für die reine und angewandte Mathematik 2008 (2008), Nr. 619
eng
Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden. Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/2832022-12-02T18:18:51Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Lifetime degradation and regeneration in multicrystalline silicon under illumination at elevated temperature
Bredemeier, Dennis
Walter, Dominic
Herlufsen, Sandra
Schmidt, Jan
Illumination
Semiconductor device fabrication
Solar cells
Crystal defects
Carrier lifetimes
Kristalldefekt
Solarzellen
ddc:530
Solarzelle
Gitterbaufehler
Halbleiterbauelement
Lebensdauer
Beleuchtung
We examine the carrier lifetime evolution of block-cast multicrystalline silicon (mc-Si) wafers under illumination (100 mW/cm2) at elevated temperature (75◦C). Samples are treated with different process steps typically applied in industrial solar cell production. We observe a pronounced degradation in lifetime after rapid thermal annealing (RTA) at 900◦C. However, we detect only a weak lifetime instability in mc-Si wafers which are TA-treated at 650◦C. After completion of the degradation, the lifetime is observed to recover and finally reaches carrier lifetimes comparable to the initial state. To explain the observed lifetime evolution, we suggest a defect model, where metal precipitates in the mc-Si bulk dissolve during the RTA treatment.
German State of Lower Saxony
German Federal Ministra of Economics and Energy
SolarLIFE/0325763C
status-type:publishedVersion
Melville, NY : American Institute of Physics
2016
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/261
http://www.repo.uni-hannover.de/handle/123456789/283
DOI:http://dx.doi.org/10.1063/1.4944839
ESSN:2158-3226
AIP Advances 6 (2016), Nr. 3
AIP Advances 6 (2016), Nr. 035119
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/2892022-12-02T15:17:15Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Sasakian quiver gauge theories and instantons on cones over lens 5-spaces
Lechtenfeld, Olaf
Popov, Alexander D.
Sperling, Marcus
Szabo, Richard J.
Conformal Field-Theories
Yang-Mills Connections
Stable Vector-Bundles
Einstein Manifolds
Dimensions
ddc:530
We consider SU(3)-equivariant dimensional reduction of Yang Mills theory over certain cyclic orbifolds of the 5-sphere which are Sasaki-Einstein manifolds. We obtain new quiver gauge theories extending those induced via reduction over the leaf spaces of the characteristic foliation of the Sasaki-Einstein structure, which are projective planes. We describe the Higgs branches of these quiver gauge theories as moduli spaces of spherically symmetric instantons which are SU(3)-equivariant solutions to the Hermitian Yang-Mills equations on the associated Calabi-Yau cones, and further compare them to moduli spaces of translationally-invariant instantons on the cones. We provide an explicit unified construction of these moduli spaces as Kahler quotients and show that they have the same cyclic orbifold singularities as the cones over the lens 5-spaces.
status-type:publishedVersion
Amsterdam : Elsevier Science Bv
2015-10
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/267
http://www.repo.uni-hannover.de/handle/123456789/289
DOI:http://dx.doi.org/10.1016/j.nuclphysb.2015.09.001
ISSN:0550-3213
ESSN:1873-1562
Nuclear Physics B 899 (2015)
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3142022-12-02T15:17:13Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersionddc:610ddc:510ddc:570
Scanning Laser Optical Tomography Resolves Structural Plasticity during Regeneration in an Insect Brain
Eickhoff, Rene
Lorbeer, Raoul-Amadeus
Scheiblich, Hannah
Heisterkamp, Alexander
Meyer, Heiko
Stern, Michael
Bicker, Gerd
projection tomography
schistocerca-gregaria
gene-expression
mushroom bodies
axonal regeneration
locusta-migratoria
tympanal nerve
desert locust
antennal lobe
microscopy
ddc:610
ddc:570
ddc:510
ddc:530
Background: Optical Projection Tomography (OPT) is a microscopic technique that generates three dimensional images from whole mount samples the size of which exceeds the maximum focal depth of confocal laser scanning microscopes. As an advancement of conventional emission-OPT, Scanning Laser Optical Tomography (SLOTy) allows simultaneous detection of fluorescence and absorbance with high sensitivity. In the present study, we employ SLOTy in a paradigm of brain plasticity in an insect model system. Methodology: We visualize and quantify volumetric changes in sensory information procession centers in the adult locust, Locusta migratoria. Olfactory receptor neurons, which project from the antenna into the brain, are axotomized by crushing the antennal nerve or ablating the entire antenna. We follow the resulting degeneration and regeneration in the olfactory centers (antennal lobes and mushroom bodies) by measuring their size in reconstructed SLOTy images with respect to the untreated control side. Within three weeks post treatment antennal lobes with ablated antennae lose as much as 60% of their initial volume. In contrast, antennal lobes with crushed antennal nerves initially shrink as well, but regain size back to normal within three weeks. The combined application of transmission-and fluorescence projections of Neurobiotin labeled axotomized fibers confirms that recovery of normal size is restored by regenerated afferents. Remarkably, SLOTy images reveal that degeneration of olfactory receptor axons has a trans-synaptic effect on second order brain centers and leads to size reduction of the mushroom body calyx. Conclusions: This study demonstrates that SLOTy is a suitable method for rapid screening of volumetric plasticity in insect brains and suggests its application also to vertebrate preparations.
DFG/REBIRTH
status-type:publishedVersion
San Francisco : Public Library Science
2012-07-19
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/292
http://www.repo.uni-hannover.de/handle/123456789/314
DOI:http://dx.doi.org/10.1371/journal.pone.0041236
ESSN:1932-6203
PLoS ONE 7 (2012), Nr. 7
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3212022-12-02T15:17:13Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessstatus-type:publishedVersionddc:600
Tile-Based Two-Dimensional Phase Unwrapping for Digital Holography Using a Modular Framework
Antonopoulos, Georgios C.
Steltner, Benjamin
Heisterkamp, Alexander
Ripken, Tammo
Meyer, Heiko
Zhang, Heye
algorithms
holography
polynomial
Gaussian noise
linear algebra
physical mapping
magnetic resonance imaging
machine learning algorithms
ddc:600
A variety of physical and biomedical imaging techniques, such as digital holography, interferometric synthetic aperture radar (InSAR), or magnetic resonance imaging (MRI) enable measurement of the phase of a physical quantity additionally to its amplitude. However, the phase can commonly only be measured modulo 2π, as a so called wrapped phase map. Phase unwrapping is the process of obtaining the underlying physical phase map from the wrapped phase. Tile-based phase unwrapping algorithms operate by first tessellating the phase map, then unwrapping individual tiles, and finally merging them to a continuous phase map. They can be implemented computationally efficiently and are robust to noise. However, they are prone to failure in the presence of phase residues or erroneous unwraps of single tiles. We tried to overcome these shortcomings by creating novel tile unwrapping and merging algorithms as well as creating a framework that allows to combine them in modular fashion. To increase the robustness of the tile unwrapping step, we implemented a model-based algorithm that makes efficient use of linear algebra to unwrap individual tiles. Furthermore, we adapted an established pixel-based unwrapping algorithm to create a quality guided tile merger. These original algorithms as well as previously existing ones were implemented in a modular phase unwrapping C++ framework. By examining different combinations of unwrapping and merging algorithms we compared our method to existing approaches. We could show that the appropriate choice of unwrapping and merging algorithms can significantly improve the unwrapped result in the presence of phase residues and noise. Beyond that, our modular framework allows for efficient design and test of new tile-based phase unwrapping algorithms. The software developed in this study is freely available.
status-type:publishedVersion
San Francisco : Public Library Science
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/299
http://www.repo.uni-hannover.de/handle/123456789/321
DOI:http://dx.doi.org/10.1371/journal.pone.0143186
ESSN:1932-6204
PLoS ONE 10 (2015), Nr. 11
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3702022-12-02T15:12:31Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
N=4 supersymmetric AdS(5) vacua and their moduli spaces
Louis, Jan
Triendl, Hagen
Zagermann, Marco
Maxwell-Einstein Supergravity
Gauged Supergravity
5 Dimensions
Field-Theories
Multiplets
Manifolds
Spectrum
Gaugings
Extended Supersymmetry
Supergravity Models
Ads-Cft Correspondence
ddc:530
We classify the N = 4 supersymmetric AdS(5) backgrounds that arise as solutions of five-dimensional N = 4 gauged supergravity. We express our results in terms of the allowed embedding tensor components and identify the structure of the associated gauge groups. We show that the moduli space of these AdS vacua is of the form SU(1, m)/ (U(1) x SU(m)) and discuss our results regarding holographically dual N = 2 SCFTs and their conformal manifolds.
status-type:publishedVersion
New York : Springer
2015-10-13
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/347
http://www.repo.uni-hannover.de/handle/123456789/370
DOI:http://dx.doi.org/10.1007/JHEP10(2015)083
ISSN:1029-8479
ESSN:1029-8479
Journal Of High Energy Physics 2015 (2015), Nr. 10
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3712022-12-02T15:12:31Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Off-diagonal ekpyrotic scenarios and equivalence of modified, massive and/or Einstein gravity
Vacaru, Sergiu I.
Massive gravity
Modified gravity
Off-diagonal cosmological solutions
Ekpyrotic and little rip universe
ddc:530
Using our anholonomic frame deformation method, we show how generic off-diagonal cosmological solutions depending, in general, on all spacetime coordinates and undergoing a phase of ultra-slow contraction can be constructed in massive gravity. In this paper, there are found and studied new classes of locally anisotropic and (in)homogeneous cosmological metrics with open and closed spatial geometries. The late time acceleration is present due to effective cosmological terms induced by nonlinear off-diagonal interactions and graviton mass. The off-diagonal cosmological metrics and related Stückelberg fields are constructed in explicit form up to nonholonomic frame transforms of the Friedmann–Lamaître–Robertson–Walker (FLRW) coordinates. We show that the solutions include matter, graviton mass and other effective sources modeling nonlinear gravitational and matter fields interactions in modified and/or massive gravity, with polarization of physical constants and deformations of metrics, which may explain certain dark energy and dark matter effects. There are stated and analyzed the conditions when such configurations mimic interesting solutions in general relativity and modifications and recast the general Painlevé–Gullstrand and FLRW metrics. Finally, we elaborate on a reconstruction procedure for a subclass of off-diagonal cosmological solutions which describe cyclic and ekpyrotic universes, with an emphasis on open issues and observable signatures.
IDEI/PN-II-ID-PCE-2011-3-0256
status-type:publishedVersion
Amsterdam : Elsevier
2016
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/348
http://www.repo.uni-hannover.de/handle/123456789/371
DOI:http://dx.doi.org/10.1016/j.physletb.2015.11.024
ISSN:0370-2693
Physics Letters B 752 (2016)
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3722022-12-02T15:17:15Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Yang–Mills solutions and dyons on cylinders over coset spaces with Sasakian structure
Tormählen, Maike
Nuclear Physics
Sasakian manifolds
Yang–Mills equation
ddc:530
We present solutions of the Yang–Mills equation on cylinders R×G/HR×G/H over coset spaces of odd dimension 2m+12m+1 with Sasakian structure. The gauge potential is assumed to be SU(m)SU(m)-equivariant, parameterized by two real, scalar-valued functions. Yang–Mills theory with torsion in this setup reduces to the Newtonian mechanics of a point particle moving in R2R2 under the influence of an inverted potential. We analyze the critical points of this potential and present an analytic as well as several numerical finite-action solutions. Apart from the Yang–Mills solutions that constitute SU(m)SU(m)-equivariant instanton configurations, we construct periodic sphaleron solutions on S1×G/HS1×G/H and dyon solutions on iR×G/HiR×G/H.
status-type:publishedVersion
Amsterdam : Elsevier
2016
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/349
http://www.repo.uni-hannover.de/handle/123456789/372
DOI:http://dx.doi.org/10.1016/j.nuclphysb.2015.11.013
ISSN:0550-3213
ESSN:1873-1562
Nuclear Physics B 902 (2016)
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3732022-12-02T15:12:31Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Instantons on Calabi–Yau cones
Sperling, Marcus
Sasakian geometry
Hermitian Yang–Mills instantons
Holomorphic structure
Nuclear physics
ddc:530
The Hermitian Yang–Mills equations on certain vector bundles over Calabi–Yau cones can be reduced to a set of matrix equations; in fact, these are Nahm-type equations. The latter can be analysed further by generalising arguments of Donaldson and Kronheimer used in the study of the original Nahm equations. Starting from certain equivariant connections, we show that the full set of instanton equations reduce, with a unique gauge transformation, to the holomorphicity condition alone.
status-type:publishedVersion
Amsterdam : Elsevier
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/350
http://www.repo.uni-hannover.de/handle/123456789/373
DOI:http://dx.doi.org/10.1016/j.nuclphysb.2015.10.014
ISSN:0550-3213
ESSN:1873-1562
Nuclear Physics B 901 (2015)
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3742022-12-02T15:15:03Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
A Calogero formulation for four-dimensional black-hole microstates
Lechtenfeld, Olaf
Nampuri, Suresh
black hole
physics
Calogero dynamics
AdS2
ddc:530
We extract the leading-order entropy of a four-dimensional extremal black hole in N=2N=2 ungauged supergravity by formulating the CFT1 that is holographically dual to its near-horizon AdS2 geometry, in terms of a rational Calogero model with a known counting formula for the degeneracy of states in its Hilbert space.
FCT–DFRH–Bolsa/SFRH/BPD/101955/2014
status-type:publishedVersion
Amsterdam : Elsevier
2016
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/351
http://www.repo.uni-hannover.de/handle/123456789/374
DOI:http://dx.doi.org/10.1016/j.physletb.2015.11.083
ISSN:0370-2693
Physics Letters B 753 (2016)
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3752022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Measurement of the doubly-polarized He3→(γ→,n)pp reaction at 16.5 MeV and its implications for the GDH sum rule
Laskaris, G.
Yan X.
Mueller, J.M.
Zimmerman, W.R.
Xiong, W.
Ahmed, M.W.
Averett, T.
Chu, P.-H.
Deltuva, A.
Flower, C.
Fonseca, A.C.
Gao, H.
Golak, J.
Heideman, J.N.
Karwowski, H.J.
Meziane, M.
Sauer, P.U.
Skibiński, R.
Strakovsky, I.I.
Weller, H.R.
Witała, H.
Wu, Y.K.
GDH sum rule
Polarized 3He
Photoabsorption
Polarization observables
ddc:530
We report new measurements of the double-polarized photodisintegration of 3He at an incident photon energy of 16.5 MeV, carried out at the High Intensity γ-ray Source (HIγS) facility located at Triangle Universities Nuclear Laboratory (TUNL). The spin-dependent double-differential cross sections and the contribution from the three-body channel to the Gerasimov–Drell–Hearn (GDH) integrand were extracted and compared with the state-of-the-art three-body calculations. The calculations, which include the Coulomb interaction and are in good agreement with the results of previous measurements at 12.8 and 14.7 MeV, deviate from the new cross section results at 16.5 MeV. The GDH integrand was found to be about one standard deviation larger than the maximum value predicted by the theories.
U.S. DOE/DE-FG02-03ER41-231
U.S. DOE/DE-FG02-03ER41-033
U.S. DOE/DE-FG02-03ER41-041
Duke University
PNSC/DEC-2013/10/M/ST2/00420
status-type:publishedVersion
Amsterdam : Elsevier
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/352
http://www.repo.uni-hannover.de/handle/123456789/375
DOI:http://dx.doi.org/10.1016/j.physletb.2015.09.065
ISSN:0370-2693
Physics Letters B 750 (2015)
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3762022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
The tetrahexahedric angular Calogero model
Correa, Francisco
Lechtenfeld, Olaf
Integrable Field Theories
Conformal and WSymmetryM
Discrete and Finite Symmetries
Integrable Hierarchies
ddc:530
The spherical reduction of the rational Calogero model (of type A n−1 and after removing the center of mass) is considered as a maximally superintegrable quantum system, which describes a particle on the (n−2)-sphere subject to a very particular potential. We present a detailed analysis of the simplest non-separable case, n=4, whose potential is singular at the edges of a spherical tetrahexahedron. A complete set of independent conserved charges and of Hamiltonian intertwiners is constructed, and their algebra is elucidated. They arise from the ring of polynomials in Dunkl-deformed angular momenta, by classifying the subspaces invariant and antiinvariant under all Weyl reflections, respectively.
Alexander von Humboldt Foundation/CHL 1153844 STP
DFG/LE 838/12-1
status-type:publishedVersion
New York : Springer
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/353
http://www.repo.uni-hannover.de/handle/123456789/376
DOI:http://dx.doi.org/10.1007/JHEP10(2015)191
ISSN:1126-6708
ESSN:1029-8479
Journal of High Energy Physics 2015 (2015), Nr. 10
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3772022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Sigma models for genuinely non-geometric backgrounds
Chatzistavrakidis, Athanasios
Jonke, Larisa
Lechtenfeld, Olaf
Sigma Models
Differential and Algebraic Geometry
String Duality
Flux compactifications
ddc:530
The existence of genuinely non-geometric backgrounds, i.e. ones without geometric dual, is an important question in string theory. In this paper we examine this question from a sigma model perspective. First we construct a particular class of Courant algebroids as protobialgebroids with all types of geometric and non-geometric fluxes. For such structures we apply the mathematical result that any Courant algebroid gives rise to a 3D topological sigma model of the AKSZ type and we discuss the corresponding 2D field theories. It is found that these models are always geometric, even when both 2-form and 2-vector fields are neither vanishing nor inverse of one another. Taking a further step, we suggest an extended class of 3D sigma models, whose world volume is embedded in phase space, which allow for genuinely non-geometric backgrounds. Adopting the doubled formalism such models can be related to double field theory, albeit from a world sheet perspective.
status-type:publishedVersion
New York : Springer
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/354
http://www.repo.uni-hannover.de/handle/123456789/377
DOI:http://dx.doi.org/10.1007/JHEP11(2015)182
ISSN:1126-6708
ESSN:1029-8479
Journal of High Energy Physics 2015 (2015), Nr. 11
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3782022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
T-duality without isometry via extended gauge symmetries of 2D sigma models
Chatzistavrakidis, Athanasios
Deser, Andreas
Jonke, Larisa
Gauge Symmetry
String Duality
Sigma Models
ddc:530
Target space duality is one of the most profound properties of string theory. However it customarily requires that the background fields satisfy certain invariance conditions in order to perform it consistently; for instance the vector fields along the directions that T-duality is performed have to generate isometries. In the present paper we examine in detail the possibility to perform T-duality along non-isometric directions. In particular, based on a recent work of Kotov and Strobl, we study gauged 2D sigma models where gauge invariance for an extended set of gauge transformations imposes weaker constraints than in the standard case, notably the corresponding vector fields are not Killing. This formulation enables us to follow a procedure analogous to the derivation of the Buscher rules and obtain two dual models, by integrating out once the Lagrange multipliers and once the gauge fields. We show that this construction indeed works in non-trivial cases by examining an explicit class of examples based on step 2 nilmanifolds.
Alexander von Humboldt Foundation
Croatian Science Foundation/IP-2014-09-3258
status-type:publishedVersion
New York : Springer
2016
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/355
http://www.repo.uni-hannover.de/handle/123456789/378
DOI:http://dx.doi.org/10.1007/JHEP01(2016)154
ISSN:1126-6708
ESSN:1029-8479
Journal of High Energy Physics 2016 (2016), Nr. 1
eng
CC BY 4.0 Unported
http://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3912022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
New design of electrostatic mirror actuators for application in high-precision interferometry
Wittel, H.
Hild, Stefan
Bergmann, Gerald
Danzmann, Karsten
Strain, Kenneth A.
interferometry
actuator
electrostatic drive
ddc:530
We describe a new geometry for electrostatic actuators to be used in sensitive laser interferometers, suited for prototype and table top experiments related to gravitational wave detection with mirrors of 100 g or less. The arrangement consists of two plates at the sides of the mirror (test mass), and therefore does not reduce its clear aperture as a conventional electrostatic drive (ESD) would do. Using the sample case of the AEI-10 m prototype interferometer, we investigate the actuation range and the influence of the relative misalignment of the ESD plates with respect to the test mass. We find that in the case of the AEI-10 m prototype interferometer, this new kind of ESD could provide a range of 0.28 mu m when operated at a voltage of 1 kV. In addition, the geometry presented is shown to provide a reduction factor of about 100 in the magnitude of the actuator motion coupling to the test mass displacement. We show that therefore in the specific case of the AEI-10 m interferometer, it is possible to mount the ESD actuators directly on the optical table without spoiling the seismic isolation performance of the triple stage suspension of the main test masses.
Max Planck Society
ERC/ERC-2012-StG/307245
Science and Technology Facilities Council (STFC)/ST/L000946/1
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-09-10
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/368
http://www.repo.uni-hannover.de/handle/123456789/391
DOI:http://dx.doi.org/10.1088/0264-9381/32/17/175021
ISSN:0264-9381
ESSN:1361-6382
Classical and Quantum Gravity 32 (2015), Nr. 17
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3922022-12-02T15:15:03Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Detecting metrologically useful entanglement in the vicinity of Dicke states
Apellaniz, Iagoba
Lücke, Bernd
Peise, Jan
Klempt, Carsten
Toth, Geza
quantum Fisher information
quantum metrology
quantum entanglement
Dicke states
horne-zeilinger entanglement
quantum-enhanced metrology
heisenberg limit
multipartite entanglement
precision limit
trapped ions
spectroscopy
light
atoms
ddc:530
We present a method to verify the metrological usefulness of noisy Dicke states of a particle ensemble with only a few collective measurements, without the need for a direct measurement of the sensitivity. Our method determines the usefulness of the state for the usual protocol for estimating the angle of rotation with Dicke states, which is based on the measurement of the second moment of a total spin component. It can also be used to detect entangled states that are useful for quantum metrology. We apply our method to recent experimental results.
EU/ERC/Starting Grant 258647/GEDENTQOPT
EU/CHIST-ERA QUASAR
EU/MINECO/FIS2012-36673-C03-03
Basque Government/IT4720-10
UPV/EHU/UFI 11/55
OTKA/K83858
QUEST
EMRP
DFG/Research Training Group 1729
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-08-13
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/369
http://www.repo.uni-hannover.de/handle/123456789/392
DOI:http://dx.doi.org/10.1088/1367-2630/17/8/083027
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3932022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Mixing of 0(+) and 0(-) observed in the hyperfine and Zeeman structure of ultracold Rb-2 molecules
Deiss, Markus
Drews, Bjoern
Denschlag, Johannes Hecker
Tiemann, Eberhard
ultracold molecules
spectroscopy
dipole transitions
hyperfine structure
Zeeman effect
spin-orbit coupling
coupled channel calculations
coupled electronic states
spectroscopy
nak
k-2
resolution
triplet
ddc:530
We study the combination of the hyperfine and Zeeman structure in the spin-orbit coupled A(1)Sigma(+)(u) = b(3)Pi(u) complex of Rb-87(2). For this purpose, absorption spectroscopy at a magnetic field around B = 1000 G is carried out. We drive optical dipole transitions from the lowest rotational state of an ultracold Feshbach molecule to various vibrational levels with 0(+) symmetry of the A - b complex. In contrast to previous measurements with rotationally excited alkali-dimers, we do not observe equal spacings of the hyperfine levels. In addition, the spectra vary substantially for different vibrational quantum numbers, and exhibit large splittings of up to 160 MHz, unexpected for 0(+) states. The level structure is explained to be a result of the repulsion between the states 0(+) and 0(-) of b(3)Pi(u), coupled via hyperfine and Zeeman interactions. In general, 0(-) and 0(+) have a spin-orbit induced energy spacing Delta, that is different for the individual vibrational states. From each measured spectrum we are able to extract Delta, which otherwise is not easily accessible in conventional spectroscopy schemes. We obtain values of Delta in the range of +/- 100 GHz which can be described by coupled channel calculations if a spin-orbit coupling is introduced that is different for 0(-) and 0(+) of b(3)Pi(u).
DFG
Ministry of Science and Culture of Lower Saxony, Germany
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-08-10
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/370
http://www.repo.uni-hannover.de/handle/123456789/393
DOI:http://dx.doi.org/10.1088/1367-2630/17/8/083032
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3942022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
The renormalization group via statistical inference
Beny, Cedric
Osborne, Tobias J.
quantum information
quantum field theory
distinguishability metrics
Gaussian states
entropy
information
physics
theorem
ddc:530
In physics, one attempts to infer the rules governing a system given only the results of imperfect measurements. Hence, microscopic theories may be effectively indistinguishable experimentally. We develop an operationally motivated procedure to identify the corresponding equivalence classes of states, and argue that the renormalization group (RG) arises from the inherent ambiguities associated with the classes: one encounters flow parameters as, e.g., a regulator, a scale, or a measure of precision, which specify representatives in a given equivalence class. This provides a unifying framework and reveals the role played by information in renormalization. We validate this idea by showing that it justifies the use of low-momenta n-point functions as statistically relevant observables around a Gaussian hypothesis. These results enable the calculation of distinguishability in quantum field theory. Our methods also provide a way to extend renormalization techniques to effective models which are not based on the usual quantum-field formalism, and elucidates the relationships between various type of RG.
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-08-05
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/371
http://www.repo.uni-hannover.de/handle/123456789/394
DOI:http://dx.doi.org/10.1088/1367-2630/17/8/083005
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3952022-12-02T15:19:56Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
A high-flux BEC source for mobile atom interferometers (vol 17, 065001, 2015)
Rudolph, Jan
Herr, Waldemar
Grzeschik, Christoph
Sternke, Tammo
Grote, Alexander
Popp, Manuel
Becker, Dennis
Muentinga, Hauke
Ahlers, Holger
Peters, Achim
Laemmerzahl, Claus
Sengstock, Klaus
Gaaloul, Naceur
Ertmer, Wolfgang
Rasel, Ernst Maria
equivalence principle
quantum sensors
Bose-Einstein condensates
atom interferometry
microgravity
ddc:530
Erratum to: A high-flux BEC source for mobile atom interferometers in: New Journal of Physics 17 (2015) 065001
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-07-09
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/372
http://www.repo.uni-hannover.de/handle/123456789/395
Rudolph, Jan; Herr, Waldemar; Grzeschik, Christoph; Sternke, Tammo; Grote, Alexander et al.: A high-flux BEC source for mobile atom interferometers. In: New Journal of Physics 17 (2015), 65001. DOI: http://dx.doi.org/10.1088/1367-2630/17/6/065001
DOI:http://dx.doi.org/10.1088/1367-2630/17/7/079601
ESSN:1367-2630
New Journal Of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3962022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Continuum tensor network field states, path integral representations and spatial symmetries
Jennings, David
Brockt, Christoph
Haegeman, Jutho
Osborne, Tobias J.
Verstraete, Frank
many-body physics
quantum fields
quantum information theory
matrix renormalization-group
product states
feynman
ddc:530
A natural way to generalize tensor network variational classes to quantum field systems is via a continuous tensor contraction. This approach is first illustrated for the class of quantum field states known as continuous matrix-product states (cMPS). As a simple example of the path-integral representation we show that the state of a dynamically evolving quantum field admits a natural representation as a cMPS. A completeness argument is also provided that shows that all states in Fock space admit a cMPS representation when the number of variational parameters tends to infinity. Beyond this, we obtain a well-behaved field limit of projected entangled-pair states (PEPS) in two dimensions that provide an abstract class of quantum field states with natural symmetries. We demonstrate how symmetries of the physical field state are encoded within the dynamics of an auxiliary field system of one dimension less. In particular, the imposition of Euclidean symmetries on the physical system requires that the auxiliary system involved in the class' definition must be Lorentz-invariant. The physical field states automatically inherit entropy area laws from the PEPS class, and are fully described by the dissipative dynamics of a lower dimensional virtual field system. Our results lie at the intersection many-body physics, quantum field theory and quantum information theory, and facilitate future exchanges of ideas and insights between these disciplines.
EU/QUERG
EU/QFTCMPS
FWF/SFB/FoQuS
FWF/SFB/ViCoM
EXC 201 Quantum Engineering and Space-Time Research.
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-06-29
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/373
http://www.repo.uni-hannover.de/handle/123456789/396
DOI:http://dx.doi.org/10.1088/1367-2630/17/6/063039
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3972022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
The 100th anniversary of the four-point probe technique: the role of probe geometries in isotropic and anisotropic systems
Miccoli, Ilio
Edler, Frederik
Pfnür, Herbert
Tegenkamp, Christoph
bulk and surface resistivity
four-point probe techniques
correction factor
nanostructures
semiconductor sheet resistivity
finite contacts
square sample
hall plate
conductivity measurements
electrical-resistivity
4-probe resistances
van
electrodes
extension
ddc:530
The electrical conductivity of solid-state matter is a fundamental physical property and can be precisely derived from the resistance measured via the four-point probe technique excluding contributions from parasitic contact resistances. Over time, this method has become an interdisciplinary characterization tool in materials science, semiconductor industries, geology, physics, etc, and is employed for both fundamental and application-driven research. However, the correct derivation of the conductivity is a demanding task which faces several difficulties, e.g. the homogeneity of the sample or the isotropy of the phases. In addition, these sample-specific characteristics are intimately related to technical constraints such as the probe geometry and size of the sample. In particular, the latter is of importance for nanostructures which can now be probed technically on very small length scales. On the occasion of the 100th anniversary of the four-point probe technique, introduced by Frank Wenner, in this review we revisit and discuss various correction factors which are mandatory for an accurate derivation of the resistivity from the measured resistance. Among others, sample thickness, dimensionality, anisotropy, and the relative size and geometry of the sample with respect to the contact assembly are considered. We are also able to derive the correction factors for 2D anisotropic systems on circular finite areas with variable probe spacings. All these aspects are illustrated by state-of-the-art experiments carried out using a four-tip STM/SEM system. We are aware that this review article can only cover some of the most important topics. Regarding further aspects, e.g. technical realizations, the influence of inhomogeneities or different transport regimes, etc, we refer to other review articles in this field.
DFG/FOR1700
DFG/Te 386/9-1
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-06-10
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/374
http://www.repo.uni-hannover.de/handle/123456789/397
DOI:http://dx.doi.org/10.1088/0953-8984/27/22/223201
ISSN:0953-8984
ESSN:1361-648X
Journal of Physics - Condensed Matter 27 (2015), Nr. 22
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3982022-12-02T15:09:33Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
A high-flux BEC source for mobile atom interferometers
Rudolph, Jan
Herr, Waldemar
Grzeschik, Christoph
Sternke, Tammo
Grote, Alexander
Popp, Manuel
Becker, Dennis
Muentinga, Hauke
Ahlers, Holger
Peters, Achim
Laemmerzahl, Claus
Sengstock, Klaus
Gaaloul, Naceur
Ertmer, Wolfgang
Rasel, Ernst Maria
equivalence principle
quantum sensors
Bose-Einstein condensates
atom interferometry
microgravity
bose-einstein condensation
matter-wave interferometry
magnetooptical trap
chip
ddc:530
Quantum sensors based on coherent matter-waves are precise measurement devices whose ultimate accuracy is achieved with Bose-Einstein condensates (BECs) in extended free fall. This is ideally realized in microgravity environments such as drop towers, ballistic rockets and space platforms. However, the transition from lab-based BEC machines to robust and mobile sources with comparable performance is a challenging endeavor. Here we report on the realization of a miniaturized setup, generating a flux of 4x10(5) quantum degenerate Rb-87 atoms every 1.6 s. Ensembles of 1 x 10(5) atoms can be produced at a 1 Hz rate. This is achieved by loading a cold atomic beam directly into a multi-layer atom chip that is designed for efficient transfer from laser-cooled to magnetically trapped clouds. The attained flux of degenerate atoms is on par with current lab-based BEC experiments while offering significantly higher repetition rates. Additionally, the flux is approaching those of current interferometers employing Raman-type velocity selection of laser-cooled atoms. The compact and robust design allows for mobile operation in a variety of demanding environments and paves the way for transportable high-precision quantum sensors.
German Space Agency (DLR)
Federal Ministry for Economic Affairs and Energy (BMWi)
BMWi/DLR 50 1131-1137
Centre for Quantum Engineering and Space-Time Research (QUEST)
Hannover School for Laser, Optics and Space-Time Research (HALOSTAR)
DFG/SFB/geo-Q
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-06-01
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/375
http://www.repo.uni-hannover.de/handle/123456789/398
DOI:http://dx.doi.org/10.1088/1367-2630/17/6/065001
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/3992022-12-02T15:19:54Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Universality of weakly bound dimers and Efimov trimers close to Li-Cs Feshbach resonances
Ulmanis, J.
Haefner, S.
Pires, R.
Kuhnle, E. D.
Weidemueller, M.
Tiemann, Eberhard
Efimov
universal dimers
Feshbach resonances
Bose-Fermi mixtures
ultracold gases
few-body systems
ultracold molecules
scattering length
polarons
physics
mixture
atoms
ddc:530
We study the interspecies scattering properties of ultracold Li-Cs mixtures in their two energetically lowest spin channels in the magnetic field range between 800 and 1000 G. Close to two broad Feshbach resonances (FR) we create weakly bound LiCs dimers by radio-frequency association and measure the dependence of their binding energy on the external magnetic field strength. Based on the binding energies and complementary atom loss spectroscopy of three other Li-Cs s-wave FRs we construct precise molecular singlet and triplet electronic ground state potentials using a coupled-channels calculation. We extract the Li-Cs interspecies scattering length as a function of the external field and obtain almost a ten-fold improvement in the precision of the values for the pole positions and widths of the s-wave FRs as compared to our previous work (Pires et al 2014 Phys. Rev. Lett. 112 250404). We discuss implications on the Efimov scenario and the universal geometric scaling for LiCsCs trimers.
Heidelberg Center for Quantum Dynamics
IMPRS-QD
DAAD
Baden-Württemberg Stiftung
Volkswagen-Stiftung
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-05-07
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/376
http://www.repo.uni-hannover.de/handle/123456789/399
DOI:http://dx.doi.org/10.1088/1367-2630/17/5/055009
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4002022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Quantum Otto heat engine based on a multiferroic chain working substance
Azimi, M.
Chotorlishvili, L.
Mishra, S.K.
Vekua, Teimuraz
Huebner, W.
Berakdar, J.
quantum heat engine
quantum entanglement
frustrated spin chain
multiferroic system
polarization
colloquium
physics
oxides
ddc:530
We study a quantum Otto engine operating on the basis of a helical spin-1/2 multiferroic chain with strongly coupled magnetic and ferroelectric order parameters. The presence of a finite spin chirality in the working substance enables steering of the cycle by an external electric field that couples to the electric polarization. We observe a direct connection between the chirality, the entanglement and the efficiency of the engine. An electric-field dependent threshold temperature is identified, above which the pair correlations in the system, as quantified by the thermal entanglement, diminish. In contrast to the pair correlations, the collective many-body thermal entanglement is less sensitive to the electric field, and in the high temperature limit converges to a constant value. We also discuss the correlations between the threshold temperature of the pair entanglement, the spin chirality and the minimum of the fidelities in relation to the electric and magnetic fields. The efficiency of the quantum Otto cycle shows a saturation plateau with increasing electric field amplitude.
DFG/SFB/762
DFG/BE 2161/5-1
DFG/QUEST
DFG/Graduiertenkolleg/1729
DFG/SFB/TR 88
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2014-06-12
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/377
http://www.repo.uni-hannover.de/handle/123456789/400
DOI:http://dx.doi.org/10.1088/1367-2630/16/6/063018
ESSN:1367-2630
New Journal of Physics 16 (2014)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4012022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Generating a state t-design by diagonal quantum circuits
Nakata, Yoshifumi
Koashi, Masato
Murao, Mio
diagonal quantum circuit
state t-design
random states
k-designs
computation
ddc:530
We investigate protocols for generating a state t-design by using a fixed separable initial state and a diagonal-unitary t-design in the computational basis, which is a t-design of an ensemble of diagonal unitary matrices with random phases as their eigenvalues. We first show that a diagonal-unitary t-design generates a O (1/2(N))-approximate state t-design, where N is the number of qubits. We then discuss a way of improving the degree of approximation by exploiting non-diagonal gates after applying a diagonal-unitary t-design. We also show that it is necessary and sufficient to use O (log(2)(t)) -qubit gates with random phases to generate a diagonal-unitary t-design by diagonal quantum circuits, and that each multi-qubit diagonal gate can be replaced by a sequence of multi-qubit controlled-phase-type gates with discrete-valued random phases. Finally, we analyze the number of gates for implementing a diagonal-unitary t-design by non-diagonal two- and one-qubit gates. Our results provide a concrete application of diagonal quantum circuits in quantum informational tasks.
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2014-05-22
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/378
http://www.repo.uni-hannover.de/handle/123456789/401
DOI:http://dx.doi.org/10.1088/1367-2630/16/5/053043
ESSN:1367-2630
New Journal of Physics 16 (2014)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4022022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Towards a gravitational wave observatory designer: sensitivity limits of spaceborne detectors
Barke, Simon
Wang, Y.
Delgado, Juan Jose Esteban
Troebs, Michael
Heinzel, Gerhard
Danzmann, Karsten
gravitational waves
laser interferometry
shot noise
laser interferometer space antenna
LISA
eLISA
OGO
lisa
interferometers
sensors
systems
noise
Gravitationswelle
ddc:530
The most promising concept for low frequency (millihertz to hertz) gravitational wave observatories are laser interferometric detectors in space. It is usually assumed that the noise floor for such a detector is dominated by optical shot noise in the signal readout. For this to be true, a careful balance of mission parameters is crucial to keep all other parasitic disturbances below shot noise. We developed a web application that uses over 30 input parameters and considers many important technical noise sources and noise suppression techniques to derive a realistic position noise budget. It optimizes free parameters automatically and generates a detailed report on all individual noise contributions. Thus one can easily explore the entire parameter space and design a realistic gravitational wave observatory. In this document we describe the different parameters, present all underlying calculations, and compare the final observatory's sensitivity with astrophysical sources of gravitational waves. We use as an example parameters currently assumed to be likely applied to a space mission proposed to be launched in 2034 by the European Space Agency. The web application itself is publicly available on the Internet at http://spacegravity.org/designer. Future versions of the web application will incorporate the frequency dependence of different noise sources and include a more detailed model of the observatory's residual acceleration noise.
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-05-07
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/379
http://www.repo.uni-hannover.de/handle/123456789/402
DOI:http://dx.doi.org/10.1088/0264-9381/32/9/095004
ISSN:0264-9381
ESSN:1361-6382
Classical And Quantum Gravity 32 (2015), Nr. 9
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4032022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Long distance coupling of a quantum mechanical oscillator to the internal states of an atomic ensemble
Vogell, B.
Kampschulte, T.
Rakher, M.T.
Faber, A.
Treutlein, P.
Hammerer, Klemens
Zoller, P.
optomechanics
hybrid quantum system
atomic ensemble
internal state coupling
resonator
cavity
optomechanics
spin
ddc:530
We propose and investigate a hybrid optomechanical system consisting of a micro-mechanical oscillator coupled to the internal states of a distant ensemble of atoms. The interaction between the systems is mediated by a light field which allows the coupling of the two systems in a modular way over long distances. Coupling to internal degrees of freedom of atoms opens up the possibility to employ high-frequency mechanical resonators in the MHz to GHz regime, such as optomechanical crystal structures, and to benefit from the rich toolbox of quantum control over internal atomic states. Previous schemes involving atomic motional states are rather limited in both of these aspects. We derive a full quantum model for the effective coupling including the main sources of decoherence. As an application we show that sympathetic ground-state cooling and strong coupling between the two systems is possible.
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-04-22
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/380
http://www.repo.uni-hannover.de/handle/123456789/403
DOI:http://dx.doi.org/10.1088/1367-2630/17/4/043044
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4042022-12-02T15:12:30Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Position-dependent spin-orbit coupling for ultracold atoms
Su, S.-W.
Gou, S.-C.
Liu, I.-K.
Spielman, I.B.
Santos, Luis
Acus, A.
Mekys, A.
Ruseckas, J.
Juzeliunas, G.
spin-orbit coupling
Bose-Einstein condesate
frustration
stripe
vortex
neutral atoms
fields
ddc:530
We theoretically explore atomic Bose-Einstein condensates (BECs) subject to position-dependent spin-orbit coupling (SOC). This SOC can be produced by cyclically laser coupling four internal atomic ground (or metastable) states in an environment where the detuning from resonance depends on position. The resulting spin-orbit coupled BEC (SOBEC) phase separates into domains, each of which contain density modulations-stripes-aligned either along the x or y direction. In each domain, the stripe orientation is determined by the sign of the local detuning. When these stripes have mismatched spatial periods along domain boundaries, non-trivial topological spin textures form at the interface, including skyrmions-like spin vortices and anti-vortices. In contrast to vortices present in conventional rotating BECs, these spin-vortices are stable topological defects that are not present in the corresponding homogenous stripe-phase SOBECs.
Research Council of Lithuania/MIP-082/2012
Taiwan Ministry of Science and Technology/MOST 103-2112-M-018-002-MY3
Taiwan Ministry of Science and Technology/MOST 103-2923-M-007-001
DFG/GRK/1729
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-03-31
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/381
http://www.repo.uni-hannover.de/handle/123456789/404
DOI:http://dx.doi.org/10.1088/1367-2630/17/3/033045
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4052022-12-02T15:17:15Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Testing the universality of free fall with rubidium and ytterbium in a very large baseline atom interferometer
Hartwig, Jonas
Abend, Sven
Schubert, Christian
Schlippert, Dennis
Ahlers, Holger
Posso-Trujillo, Katerine
Gaaloul, Naceur
Ertmer, Wolfgang
Rasel, Ernst Maria
atom interferometry
equivalence principle
Bose-Einstein condensation
ddc:530
We propose a very long baseline atom interferometer test of Einstein's equivalence principle (EEP) with ytterbium and rubidium extending over 10m of free fall. In view of existing parametrizations of EEP violations, this choice of test masses significantly broadens the scope of atom interferometric EEP tests with respect to other performed or proposed tests by comparing two elements with high atomic numbfers. In the first step, our experimental scheme will allow us to reach an accuracy in the Eotvos ratio of 7 . 10(-13). This achievement will constrain violation scenarios beyond our present knowledge and will represent an important milestone for exploring a variety of schemes for further improvements of the tests as outlined in the paper. We will discuss the technical realisation in the new infrastructure of the Hanover Institute of Technology (HITec) and give a short overview of the requirements needed to reach this accuracy. The experiment will demonstrate a variety of techniques, which will be employed in future tests of EEP, high-accuracy gravimetry and gravity gradiometry. It includes operation of a force-sensitive atom interferometer with an alkaline earth-like element in free fall, beam splitting over macroscopic distances and novel source concepts.
DFG/SFB/geo-Q
BMWi/DLR/50WM1131.1137
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-03-20
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/382
http://www.repo.uni-hannover.de/handle/123456789/405
DOI:http://dx.doi.org/10.1088/1367-2630/17/3/035011
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4062022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Spectral self-action of THz emission from ionizing two-color laser pulses in gases
Cabrera-Granado, Eduardo
Chen, Yxing
Babushkin, Ihar
Berge, Luc
Skupin, Stefan
ultrafast nonlinear optics
photoionization
THz generation
far infrared spectroscopy
multi-color pulses
terahertz
generation
air
ddc:530
The spectrum of terahertz (THz) emission in gases via ionizing two-color femtosecond pulses is analyzed by means of a semi-analytic model and numerical simulations in 1D, 2D and 3D geometries taking into account propagation effects of both pump and THz fields. We show that produced THz signals interact with free electron trajectories and thus significantly influence further THz generation upon propagation, i.e., make the process inherently nonlocal. This self-action contributes to the observed strong spectral broadening of the generated THz field. Weshow that diffraction of the generated THz radiation is the limiting factor for the co-propagating low frequency amplitudes and thus for the self-action mechanism in 2D and 3D geometries.
PRI-AIBDE-2011-0902
DAAD-PPP-54367872
DFG/SFB/910
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-02-18
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/383
http://www.repo.uni-hannover.de/handle/123456789/406
DOI:http://dx.doi.org/10.1088/1367-2630/17/2/023060
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4072022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Generalized cluster states based on finite groups
Brell, Courtney G.
measurement-based quantum computation
fault-tolerant quantum computation
topological computation
tolerant quantum computation
error-correcting codes
classical simulations
normalizer circuits
systems
anyons
ddc:530
We define generalized cluster states based on finite group algebras in analogy to the generalization of the toric code to the Kitaev quantum double models. We do this by showing a general correspondence between systems with CSS structure and finite group algebras, and applying this to the cluster states to derive their generalization. We then investigate properties of these states including their projected entangled pair state representations, global symmetries, and relationship to the Kitaev quantum double models. We also discuss possible applications of these states.
ARC/EQuS/CE10001013
ERC/QFTCMPS
DFG/EXC201/QUEST
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015-02-10
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/384
http://www.repo.uni-hannover.de/handle/123456789/407
DOI:http://dx.doi.org/10.1088/1367-2630/17/2/023029
ESSN:1367-2630
New Journal of Physics 17 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4082022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Perturbative 2-body parent Hamiltonians for projected entangled pair states
Brell, Courtney G.
Bartlett, Stephen D.
Doherty, Andrew C.
projected entangled pair state
topological order
parent Hamiltonian
quantum
stability
systems
complexity
lattice
anyons
ddc:530
We construct parent Hamiltonians involving only local 2-body interactions for a broad class of projected entangled pair states (PEPS). Making use of perturbation gadget techniques, we define a perturbative Hamiltonian acting on the virtual PEPS space with a finite order low energy effective Hamiltonian that is a gapped, frustration-free parent Hamiltonian for an encoded version of a desired PEPS. For topologically ordered PEPS, the ground space of the low energy effective Hamiltonian is shown to be in the same phase as the desired state to all orders of perturbation theory. An encoded parent Hamiltonian for the double semion string net ground state is explicitly constructed as a concrete example.
ARC/EQuS/CE110001013
ERC/QFTCMPS
DFG/EXC201/QUEST
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2014-12-22
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/385
http://www.repo.uni-hannover.de/handle/123456789/408
DOI:http://dx.doi.org/10.1088/1367-2630/16/12/123056
ESSN:1367-2630
New Journal of Physics 16 (2014)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4092022-12-02T15:15:03Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Decoherence models for discrete-time quantum walks and their application to neutral atom experiments
Alberti, Andrea
Alt, Wolfgang
Werner, Reinhard F.
Meschede, Dieter
quantum walks
decoherence
optical lattices
floquet theory
optically trapped atoms
wigner function
space
mechanics
ddc:530
We discuss decoherence in discrete-time quantum walks in terms of a phenomenological model that distinguishes spin and spatial decoherence. We identify the dominating mechanisms that affect quantum-walk experiments realized with neutral atoms walking in an optical lattice. From the measured spatial distributions, we determine with good precision the amount of decoherence per step, which provides a quantitative indication of the quality of our quantum walks. In particular, we find that spin decoherence is the main mechanism responsible for the loss of coherence in our experiment. We also find that the sole observation of ballistic-instead of diffusive-expansion in position space is not a good indicator of the range of coherent delocalization. We provide further physical insight by distinguishing the effects of short- and long-time spin dephasing mechanisms. We introduce the concept of coherence length in the discrete-time quantum walk, which quantifies the range of spatial coherences. Unexpectedly, we find that quasi-stationary dephasing does not modify the local properties of the quantum walk, but instead affects spatial coherences. For a visual representation of decoherence phenomena in phase space, we have developed a formalism based on a discrete analogue of the Wigner function. We show that the effects of spin and spatial decoherence differ dramatically in momentum space.
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2014-12-19
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/386
http://www.repo.uni-hannover.de/handle/123456789/409
DOI:http://dx.doi.org/10.1088/1367-2630/16/12/123052
ESSN:1367-2630
New Journal of Physics 16 (2014)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4102022-12-02T15:15:03Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Design of a speed meter interferometer proof-of-principle experiment
Gräf, Christian
Barr, B.W.
Bell, A.S.
Campbell, F.
Cumming, A.V.
Danilishin, S.L.
Gordon, N.A.
Hammond, G.D.
Hennig, J.
Houston, E.A.
Huttner, S.H.
Jones, R.A.
Leavey, Sean S.
Lück, Harald
Macarthur, J.
Marwick, M.
Rigby, S.
Schilling, R.
Sorazu, B.
Spencer, A.
Steinlechner, S.
Strain, Kenneth A.
Hild, Stefan
Sagnac speed meter
quantum noise
laser interferometer
conceptual design
gravitational wave detector
QND
quantum non-demolition
gravitational-wave detection
sagnac interferometer
optical cavities
detectors
coatings
noise
Gravitationswelle
ddc:530
The second generation of large scale interferometric gravitational wave (GW) detectors will be limited by quantum noise over a wide frequency range in their detection band. Further sensitivity improvements for future upgrades or new detectors beyond the second generation motivate the development of measurement schemes to mitigate the impact of quantum noise in these instruments. Two strands of development are being pursued to reach this goal, focusing both on modifications of the well-established Michelson detector configuration and development of different detector topologies. In this paper, we present the design of the world's first Sagnac speed meter (SSM) interferometer, which is currently being constructed at the University of Glasgow. With this proof-of-principle experiment we aim to demonstrate the theoretically predicted lower quantum noise in a Sagnac interferometer compared to an equivalent Michelson interferometer, to qualify SSM for further research towards an implementation in a future generation large scale GW detector, such as the planned Einstein telescope observatory.
ERC-2012-StG/307245
Science and Technology Facilites Council (STFC)
Humboldt Foundation
International Max Planck Partnership (IMPP)
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2014-11-07
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/387
http://www.repo.uni-hannover.de/handle/123456789/410
DOI:http://dx.doi.org/10.1088/0264-9381/31/21/215009
ISSN:0264-9381
ESSN:1361-6382
Classical And Quantum Gravity 31 (2014), Nr. 21
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4112022-12-02T15:17:13Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
High-temperature superconductivity in the two-dimensional t-J model: Gutzwiller wavefunction solution
Kaczmarczyk, Jan
Buenemann, Joerg
Spalek, Jozef
t-J model
high-temperature superconductivity
Gutzwiller wave function
unconventional superconductivity
variational Monte-Carlo method
mean-field theory
dimensional fermi-surface
hubbard-model
state
transition
pseudogap
oxides
instability
competition
ansatz
ddc:530
A systematic diagrammatic expansion for Gutzwiller wavefunctions (DE-GWFs) proposed very recently is used for the description of the superconducting (SC) ground state in the two-dimensional square-lattice t–J model with the hopping electron amplitudes t (and $t^{\prime} $) between nearest (and next-nearest) neighbors. For the example of the SC state analysis we provide a detailed comparison of the methodʼs results with those of other approaches. Namely, (i) the truncated DE-GWF method reproduces the variational Monte Carlo (VMC) results and (ii) in the lowest (zeroth) order of the expansion the method can reproduce the analytical results of the standard Gutzwiller approximation (GA), as well as of the recently proposed 'grand-canonical Gutzwiller approximation' (called either GCGA or SGA). We obtain important features of the SC state. First, the SC gap at the Fermi surface resembles a ${{d}_{{{x}^{2}}-{{y}^{2}}}}$ wave only for optimally and overdoped systems, being diminished in the antinodal regions for the underdoped case in a qualitative agreement with experiment. Corrections to the gap structure are shown to arise from the longer range of the real-space pairing. Second, the nodal Fermi velocity is almost constant as a function of doping and agrees semi-quantitatively with experimental results. Third, we compare the doping dependence of the gap magnitude with experimental data. Fourth, we analyze the k-space properties of the model: Fermi surface topology and effective dispersion. The DE-GWF method opens up new perspectives for studying strongly correlated systems, as it (i) works in the thermodynamic limit, (ii) is comparable in accuracy to VMC, and (iii) has numerical complexity comparable to that of the GA (i.e., it provides the results much faster than the VMC approach).
Foundation for Polish Science (FNP)/TEAM program
National Science Centre (NCN)/MAESTRO
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2014-07-14
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/388
http://www.repo.uni-hannover.de/handle/123456789/411
DOI:http://dx.doi.org/10.1088/1367-2630/16/7/073018
ESSN:1367-2630
New Journal of Physics 16 (2014)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4122022-12-02T15:15:03Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Centre-of-mass motion in multi-particle Schrodinger-Newton dynamics
Giulini, Domenico
Grossardt, Andre
Schrodinger-Newton equation
quantum gravity
semi-classical gravity
ddc:530
We investigate the implication of the nonlinear and non-local multi-particle Schrodinger-Newton equation for the motion of the mass centre of an extended multi-particle object, giving self-contained and comprehensible derivations. In particular, we discuss two opposite limiting cases. In the first case, the width of the centre-of-mass wave packet is assumed much larger than the actual extent of the object, in the second case it is assumed much smaller. Both cases result in nonlinear deviations from ordinary free Schrodinger evolution for the centre of mass. On a general conceptual level we include some discussion in order to clarify the physical basis and intention for studying the Schrodinger-Newton equation.
QUEST
John Templeton Foundation/39530
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2014-07-08
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/389
http://www.repo.uni-hannover.de/handle/123456789/412
DOI:http://dx.doi.org/10.1088/1367-2630/16/7/075005
ESSN:1367-2630
New Journal of Physics 16 (2014)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4142022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Gaussian entanglement for quantum key distribution from a single-mode squeezing source
Eberle, Tobias
Haendchen, Vitus
Duhme, Jörg
Franz, Torsten
Furrer, Fabian
Schnabel, Roman
Werner, Reinhard F.
optical parametric-amplifier
podolsky-rosen paradox
experimental generation
efficiency
states
light
fiber
beams
ddc:530
We report the suitability of an Einstein-Podolsky-Rosen entanglement source for Gaussian continuous-variable quantum key distribution at 1550 nm. Our source is based on a single continuous-wave squeezed vacuum mode combined with a vacuum mode at a balanced beam splitter. Extending a recent security proof, we characterize the source by quantifying the extractable length of a composable secure key from a finite number of samples under the assumption of collective attacks. We show that distances in the order of 10 km are achievable with this source for a reasonable sample size despite the fact that the entanglement was generated including a vacuum mode. Our security analysis applies to all states having an asymmetry in the field quadrature variances, including those generated by superposition of two squeezed modes with different squeezing strengths.
EU/FP7/Q-ESSENCE
HALOSTAR
DFG/WE-1240/12-1
BMBF/QUOREP
Japan Society for the Promotion of Science/KAKENHI/24-02793
EU/FP7/COQUIT
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2013-05-30
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/391
http://www.repo.uni-hannover.de/handle/123456789/414
DOI:http://dx.doi.org/10.1088/1367-2630/15/5/053049
ESSN:1367-2630
New Journal of Physics 15 (2013)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4152022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
The D(D-3)-anyon chain: integrable boundary conditions and excitation spectra
Finch, Peter E.
Frahm, Holger
invariant partition-functions
non-abelian anyons
operator content
finite-size
conformal-invariance
quantum computation
critical exponents
critical systems
dynkin diagrams
lattice models
ddc:530
Chains of interacting non-Abelian anyons with local interactions invariant under the action of the Drinfeld double of the dihedral group D-3 are constructed. Formulated as a spin chain the Hamiltonians are generated from commuting transfer matrices of an integrable vertex model for periodic and braided as well as open boundaries. A different anyonic model with the same local Hamiltonian is obtained within the fusion path formulation. This model is shown to be related to an integrable fusion interaction round the face model. Bulk and surface properties of the anyon chain are computed from the Bethe equations for the spin chain. The low-energy effective theories and operator content of the models (in both the spin chain and fusion path formulation) are identified from analytical and numerical studies of the finite-size spectra. For all boundary conditions considered the continuum theory is found to be a product of two conformal field theories. Depending on the coupling constants the factors can be a Z(4) parafermion or a M-(5,M-6) minimal model.
DFG
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2013-05-22
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/392
http://www.repo.uni-hannover.de/handle/123456789/415
DOI:http://dx.doi.org/10.1088/1367-2630/15/5/053035
ESSN:1367-2630
New Journal of Physics 15 (2013)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4162022-12-02T15:15:03Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Bosonization and entanglement spectrum for one-dimensional polar bosons on disordered lattices
Deng, Xiaolong
Citro, Roberta
Orignac, Edmond
Minguzzi, Anna
Santos, Luis
density-matrix renormalization
antiferromagnetic spin-1 chain
anderson localization
insulator-transition
optical lattice
quantum fluids
phases
gases
matter
states
ddc:530
Ultra cold polar bosons in a disordered lattice potential, described by the extended Bose-Hubbard model, display a rich phase diagram. In the case of uniform random disorder one finds two insulating quantum phases-the Mott-insulator and the Haldane insulator-in addition to a superfluid and a Bose glass phase. In the case of a quasiperiodic potential, further phases are found, e.g. the incommensurate density wave, adiabatically connected to the Haldane insulator. For the case of weak random disorder we determine the phase boundaries using a perturbative bosonization approach. We then calculate the entanglement spectrum for both types of disorder, showing that it provides a good indication of the various phases.
DFG/SA1031/6
German-Israeli Foundation
DFG/EXC/QUEST
CNRS/PEPS-PTI
ERC/Handy-Q/258608
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2013-04-26
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/393
http://www.repo.uni-hannover.de/handle/123456789/416
DOI:http://dx.doi.org/10.1088/1367-2630/15/4/045023
ESSN:1367-2630
New Journal of Physics 15 (2013)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4172022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Resonant five-body recombination in an ultracold gas of bosonic atoms
Zenesini, Alessandro
Huang, Bo
Berninger, Martin
Besler, Stefan
Naegerl, Hanns-Christoph
Ferlaino, Francesca
Grimm, Rudolf
Greene, Chris H.
Stecher, Javier von
large scattering length
4-body system
body systems
states
universality
limit
ddc:530
We combine theory and experiment to investigate five-body recombination in an ultracold gas of atomic cesium at negative scattering length. A refined theoretical model, in combination with extensive laboratory tunability of the interatomic interactions, enables the five-body resonant recombination rate to be calculated and measured. The position of the new observed recombination feature agrees with a recent theoretical prediction and supports the prediction of a family of universal cluster states at negative a that are tied to an Efimov trimer.
Austrian Science Fund/FWF/P23106
US National Science Foundation
European Council/Marie Curie/LatTriCs 254987
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2013-04-22
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/394
http://www.repo.uni-hannover.de/handle/123456789/417
DOI:http://dx.doi.org/10.1088/1367-2630/15/4/043040
ESSN:1367-2630
New Journal of Physics 15 (2013)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4182022-12-02T15:19:54Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Truncation identities for the small polaron fusion hierarchy
Grabinski, Andre M.
Frahm, Holger
open-boundary-conditions
algebraic bethe-ansatz
xxz spin chain
t-q relation
functional relations
lattice models
vertex models
terms
matrices
systems
ddc:530
We study a one-dimensional lattice model of interacting spinless fermions. This model is integrable for both periodic and open boundary conditions; the latter case includes the presence of Grassmann valued non-diagonal boundary fields breaking the bulk U(1) symmetry of the model. Starting from the embedding of this model into a graded Yang-Baxter algebra, an infinite hierarchy of commuting transfer matrices is constructed by means of a fusion procedure. For certain values of the coupling constant related to anisotropies of the underlying vertex model taken at roots of unity, this hierarchy is shown to truncate giving a finite set of functional equations for the spectrum of the transfer matrices. For generic coupling constants, the spectral problem is formulated in terms of a functional (or TQ-)equation which can be solved by Bethe ansatz methods for periodic and diagonal open boundary conditions. Possible approaches for the solution of the model with generic non-diagonal boundary fields are discussed.
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2013-04-17
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/395
http://www.repo.uni-hannover.de/handle/123456789/418
DOI:http://dx.doi.org/10.1088/1367-2630/15/4/043026
ESSN:1367-2630
New Journal of Physics 15 (2013)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4192022-12-02T15:15:03Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Causal structure of the entanglement renormalization ansatz
Beny, Cedric
Physics, Multidisciplinary
ddc:530
We show that the multiscale entanglement renormalization ansatz (MERA) can be reformulated in terms of a causality constraint on discrete quantum dynamics. This causal structure is that of de Sitter space with a flat space-like boundary, where the volume of a spacetime region corresponds to the number of variational parameters it contains. This result clarifies the nature of the ansatz, and suggests a generalization to quantum field theory. It also constitutes an independent justification of the connection between MERA and hyperbolic geometry which was proposed as a concrete implementation of the AdS-CFT correspondence.
DFG/EXC/201/QUEST
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2013-02-13
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/396
http://www.repo.uni-hannover.de/handle/123456789/419
DOI:http://dx.doi.org/10.1088/1367-2630/15/2/023020
ESSN:1367-2630
New Journal of Physics 15 (2013)
eng
CC BY-NC-SA 3.0 Unported
https://creativecommons.org/licenses/by-nc-sa/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4202022-12-02T15:15:03Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Asymptotic scattering and duality in the one-dimensional three-state quantum Potts model on a lattice
Rapp, Akos
Schmitteckert, Peter
Takacs, Gabor
Zarand, Gergely
exact s-matrices
field-theory
renormalization-groups
structure constants
amplitude ratios
transverse field
dynamics
percolation
algebra
systems
ddc:530
We determine numerically the single-particle and the two-particle spectrum of the three-state quantum Potts model on a lattice by using the density matrix renormalization group method, and extract information on the asymptotic (small momentum) S-matrix of the quasiparticles. The low energy part of the finite size spectrum can be understood in terms of a simple effective model introduced in a previous work, and is consistent with an asymptotic S-matrix of an exchange form below a momentum scale p*. This scale appears to vanish faster than the Compton scale, mc, as one approaches the critical point, suggesting that a dangerously irrelevant operator may be responsible for the behaviour observed on the lattice.
Hungarian Research Fund/K73361
Hungarian Research Fund/CNK80991
Hungarian Research Fund/K75172
Romanian grant CNCSIS PN II ID-672/2008
DFG
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2013-01-28
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/397
http://www.repo.uni-hannover.de/handle/123456789/420
DOI:http://dx.doi.org/10.1088/1367-2630/15/1/013058
ESSN:1367-2630
New Journal of Physics 15 (2013)
eng
CC BY-NC-SA 3.0 Unported
https://creativecommons.org/licenses/by-nc-sa/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4212022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
A representation-free description of the Kasevich-Chu interferometer: a resolution of the redshift controversy
Schleich, Wolfgang P.
Greenberger, Daniel M.
Rasel, Ernst Maria
gravito-inertial sensors
gravitational redshift
atomic interferometry
wave interferometry
quantum-mechanics
diffraction
clocks
interference
spectroscopy
gravimeters
ddc:530
Motivated by a recent claim by Muller et al (2010 Nature 463 926-9) that an atom interferometer can serve as an atom clock to measure the gravitational redshift with an unprecedented accuracy, we provide a representation-free description of the Kasevich-Chu interferometer based on operator algebra. We use this framework to show that the operator product determining the number of atoms at the exit ports of the interferometer is a c-number phase factor whose phase is the sum of only two phases: one is due to the acceleration of the phases of the laser pulses and the other one is due to the acceleration of the atom. This formulation brings out most clearly that this interferometer is an accelerometer or a gravimeter. Moreover, we point out that in different representations of quantum mechanics such as the position or the momentum representation the phase shift appears as though it originates from different physical phenomena. Due to this representation dependence conclusions concerning an enhanced accuracy derived in a specific representation are unfounded.
German Space Agency (DLR)
BMWi/DLR 50 WM 0837
Alexander von Humboldt Stiftung
Templeton Foundation/21531
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2013-01-07
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/398
http://www.repo.uni-hannover.de/handle/123456789/421
DOI:http://dx.doi.org/10.1088/1367-2630/15/1/013007
ESSN:1367-2630
New Journal of Physics 15 (2013)
eng
CC BY-NC-SA 3.0 Unported
https://creativecommons.org/licenses/by-nc-sa/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4222022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Tomographic readout of an opto-mechanical interferometer
Kaufer, Henning
Sawadsky, Andreas
Westphal, Tobias
Friedrich, Daniel
Schnabel, Roman
quantum-noise
oscillator
ddc:530
The quantum state of light changes its nature when being reflected off a mechanical oscillator due to the latter's susceptibility to radiation pressure. As a result, a coherent state can transform into a squeezed state and can get entangled with the motion of the oscillator. Full information of the state of light can only be gathered by a tomographic measurement. Here we demonstrate a tomographic interferometer readout by measuring arbitrary quadratures of the light field exiting a Michelson-Sagnac interferometer that contains a thermally excited high-quality silicon nitride membrane. A readout noise of 1.9 x 10(-16) mHz(-1/2) around the membrane's fundamental oscillation mode at 133 kHz has been achieved, going below the peak value of the standard quantum limit by a factor of 8.2 (9 dB). The readout noise was entirely dominated by shot noise in a rather broad frequency range around the mechanical resonance.
International Max Planck Research School for Gravitational Wave Astronomy (IMPRS)
QUEST
HALOSTAR
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2012-09-12
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/399
http://www.repo.uni-hannover.de/handle/123456789/422
DOI:http://dx.doi.org/10.1088/1367-2630/14/9/095018
ESSN:1367-2630
New Journal of Physics 14 (2012)
eng
CC BY-NC-SA 3.0 Unported
https://creativecommons.org/licenses/by-nc-sa/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4232022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Exciton-mediated photothermal cooling in GaAs membranes
Xuereb, Andre
Usami, Koji
Naesby, Andreas
Polzik, Eugene S.
Hammerer, Klemens
cavity
optomechanics
ddc:530
Cooling of the mechanical motion of a GaAs nano-membrane using the photothermal effect mediated by excitons was recently demonstrated by some of the authors (Usami et al 2012 Nature Phys. 8 168) and provides a clear example of the use of thermal forces to cool down mechanical motion. Here, we report on a single-free-parameter theoretical model to explain the results of this experiment which matches the experimental data remarkably well.
QUEST
EU/FET/Q-ESSENCE
EU/DARPA/QUASAR
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2012-08-29
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/400
http://www.repo.uni-hannover.de/handle/123456789/423
DOI:http://dx.doi.org/10.1088/1367-2630/14/8/085024
ESSN:1367-2630
New Journal of Physics 14 (2012)
eng
CC BY-NC-SA 3.0 Unported
https://creativecommons.org/licenses/by-nc-sa/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4242022-12-02T15:15:03Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
A proposal for self-correcting stabilizer quantum memories in 3 dimensions (or slightly less)
Brell, Courtney G.
quantum memory
topological order
topological codes
ddc:530
We propose a family of local CSS stabilizer codes as possible candidates for self-correcting quantum memories in 3D. The construction is inspired by the classical Ising model on a Sierpinski carpet fractal, which acts as a classical self-correcting memory. Our models are naturally defined on fractal subsets of a 4D hypercubic lattice with Hausdorff dimension less than 3. Though this does not imply that these models can be realized with local interactions in R3, we also discuss this possibility. The X and Z sectors of the code are dual to one another, and we show that there exists a finite temperature phase transition associated with each of these sectors, providing evidence that the system may robustly store quantum information at finite temperature.
DFG/EXC/201
ERC/QFTCMPS
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2016-01-25
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/401
http://www.repo.uni-hannover.de/handle/123456789/424
DOI:http://dx.doi.org/10.1088/1367-2630/18/1/013050
ESSN:1367-2630
New Journal of Physics 18 (2016)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4252022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersionddc:500
Disentangling the magnetic force noise contribution in LISA Pathfinder
Armano, M.
Audley, H.
Auger, G.
Baird, J.
Binetruy, P.
Born, Michael
Bortoluzzi, D.
Brandt, N.
Bursi, A.
Caleno, M.
Cavalleri, A.
Cesarini, A.
Cruise, M.
Danzmann, Karsten
Diepholz, I.
Dolesi, R.
Dunbar, N.
Ferraioli, L.
Ferroni, V.
Fitzsimons, E.
Freschi, M.
Gallegos, J.
Marirrodriga, C. Garcia
Gerndt, R.
Gesa, L.I.
Gibert, F.
Giardini, D.
Giusteri, R.
Grimani, C.
Harrison, I.
Heinzel, Gerhard
Hewitson, M.
Hollington, D.
Hueller, M.
Huesler, J.
Inchauspe, H.
Jennrich, O.
Jetzer, P.
Johlander, B.
Karnesis, N.
Kaune, B.
Korsakova, N.
Killow, C.
Lloro, I.
Maarschalkerweerd, R.
Madden, S.
Mance, D.
Martin, V.
Martin-Porqueras, F.
Mateos, I.
McNamara, P.
Mendes, J.
Mendes, L.
Moroni, A.
Nofrarias, M.
Paczkowski, S.
Perreur-Lloyd, M.
Petiteau, A.
Pivato, P.
Plagnol, E.
Prat, P.
Ragnit, U.
Ramos-Castro, J.
Reiche, J.
Perez, J. A. Romera
Robertson, D.
Rozemeijer, H.
Russano, G.
Sarra, P.
Schleicher, A.
Slutsky, J.
Sopuerta, C.F.
Sumner, T.
Texier, D.
Thorpe, J.
Trenkel, C.
Tu, H.B.
Vitale, S.
Wanner, G.
Ward, H.
Waschke, S.
Wass, P.
Wealthy, D.
Wen, S.
Weber, W.
Wittchen, A.
Zanoni, C.
Ziegler, T.
Zweifel, P.
LISA Pathfinder
Astronomy
Astrophysics
Physics, Applied
ddc:500
ddc:530
Konferenzschrift
Magnetically-induced forces on the inertial masses on-board LISA Path finder are expected to be one of the dominant contributions to the mission noise budget, accounting for up to 40%. The origin of this disturbance is the coupling of the residual magnetization and susceptibility of the test masses with the environmental magnetic field. In order to fully understand this important part of the noise model, a set of coils and magnetometers are integrated as a part of the diagnostics subsystem. During operations a sequence of magnetic excitations will be applied to precisely determine the coupling of the magnetic environment to the test mass displacement using the on-board magnetometers. Since no direct measurement of the magnetic field in the test mass position will be available, an extrapolation of the magnetic measurements to the test mass position will be carried out as a part of the data analysis activities. In this paper we show the first results on the magnetic experiments during an end-to-end LISA Path finder simulation, and we describe the methods under development to map the magnetic field on-board.
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/402
http://www.repo.uni-hannover.de/handle/123456789/425
DOI:http://dx.doi.org/10.1088/1742-6596/610/1/012024
ISSN:1742-6588
ESSN:1742-6596
Journal of Physics Conference Series 610 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4262022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersionddc:500
A Strategy to Characterize the LISA-Pathfinder Cold Gas Thruster System
Armano, M.
Audley, H.
Auger, G.
Baird, J.
Binetruy, P.
Born, Michael
Bortoluzzi, D.
Brandt, N.
Bursi, A.
Caleno, M.
Cavalleri, A.
Cesarini, A.
Cruise, M.
Danzmann, Karsten
Diepholz, I.
Dolesi, R.
Dunbar, N.
Ferraioli, L.
Ferroni, V.
Fitzsimons, E.
Freschi, M.
Gallegos, J.
Marirrodriga, C. Garcia
Gerndt, R.
Gesa, L.I.
Gibert, F.
Giardini, D.
Giusteri, R.
Grimani, C.
Harrison, I.
Heinzel, Gerhard
Hewitson, M.
Hollington, D.
Hueller, M.
Huesler, J.
Inchauspe, H.
Jennrich, O.
Jetzer, P.
Johlander, B.
Karnesis, N.
Kaune, B.
Korsakova, N.
Killow, C.
Lloro, I.
Maarschalkerweerd, R.
Madden, S.
Mance, D.
Martin, V.
Martin-Porqueras, F.
Mateos, I.
McNamara, P.
Mendes, J.
Mendes, L.
Moroni, A.
Nofrarias, M.
Paczkowski, S.
Perreur-Lloyd, M.
Petiteau, A.
Pivato, P.
Plagnol, E.
Prat, P.
Ragnit, U.
Ramos-Castro, J.
Reiche, J.
Perez, J. A. Romera
Robertson, D.
Rozemeijer, H.
Russano, G.
Sarra, P.
Schleicher, A.
Slutsky, J.
Sopuerta, C.F.
Sumner, T.
Texier, D.
Thorpe, J.
Trenkel, C.
Tu, H.B.
Vitale, S.
Wanner, G.
Ward, H.
Waschke, S.
Wass, P.
Wealthy, D.
Wen, S.
Weber, W.
Wittchen, A.
Zanoni, C.
Ziegler, T.
Zweifel, P.
LISA Pathfinder
Astronomy
Astrophysics
Physics, Applied
ddc:500
ddc:530
Konferenzschrift
The cold gas micro-propulsion system that will be used during the LISA-Pathfinder mission will be one of the most important component used to ensure the "free-fall" of the enclosed test masses. In this paper we present a possible strategy to characterize the effective direction and amplitude gain of each of the 6 thrusters of this system.
Sorbonne Paric Cite/UnivEarthS Labex
French Space Ageny (CNES)
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/403
http://www.repo.uni-hannover.de/handle/123456789/426
DOI:http://dx.doi.org/10.1088/1742-6596/610/1/012026
ISSN:1742-6588
ESSN:1742-6596
Journal of Physics Conference Series 610 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4302022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersionddc:500
In-flight thermal experiments for LISA Pathfinder: Simulating temperature noise at the Inertial Sensors
Gibert, F.
Nofrarias, M.
Armano, M.
Audley, H.
Auger, G.
Baird, J.
Binetruy, P.
Born, Michael
Bortoluzzi, D.
Brandt, N.
Bursi, A.
Caleno, M.
Cavalleri, A.
Cesarini, A.
Cruise, M.
Danzmann, Karsten
Diepholz, I.
Dolesi, R.
Dunbar, N.
Ferraioli, L.
Ferroni, V.
Fitzsimons, E.
Freschi, M.
Gallegos, J.
Garcia Marirrodriga, C.
Gerndt, R.
Gesa, L.I.
Giardini, D.
Giusteri, R.
Grimani, C.
Harrison, I.
Heinzel, Gerhard
Hewitson, M.
Hollington, D.
Hueller, M.
Huesler, J.
Inchauspe, H.
Jennrich, O.
Jetzer, P.
Johlander, B.
Karnesis, N.
Kaune, B.
Korsakova, N.
Killow, C.
Lloro, I.
Maarschalkerweerd, R.
Madden, S.
Maghami, P.
Mance, D.
Martin, V.
Martin-Porqueras, F.
Mateos, I.
McNamara, P.
Mendes, J.
Mendes, L.
Moroni, A.
Paczkowski, S.
Perreur-Lloyd, M.
Petiteau, A.
Pivato, P.
Plagnol, E.
Prat, P.
Ragnit, U.
Ramos-Castro, J.
Reiche, J.
Perez, J. A. Romera
Robertson, D.
Rozemeijer, H.
Russano, G.
Sarra, P.
Schleicher, A.
Slutsky, J.
Sopuerta, C.F.
Sumner, T.
Texier, D.
Thorpe, J.
Trenkel, C.
Tu, H.B.
Vetrugno, D.
Vitale, S.
Wanner, G.
Ward, H.
Waschke, S.
Wass, P.
Wealthy, D.
Wen, S.
Weber, W.
Wittchen, A.
Zanoni, C.
Ziegler, T.
Zweifel, P.
Astronomy & Astrophysics
Physics, Applied
ddc:500
ddc:530
Konferenzschrift
Thermal Diagnostics experiments to be carried out on board LISA Pathfinder (LPF) will yield a detailed characterisation of how temperature fluctuations affect the LTP (LISA Technology Package) instrument performance, a crucial information for future space based gravitational wave detectors as the proposed eLISA. Amongst them, the study of temperature gradient fluctuations around the test masses of the Inertial Sensors will provide as well information regarding the contribution of the Brownian noise, which is expected to limit the LTP sensitivity at frequencies close to 1mHz during some LTP experiments. In this paper we report on how these kind of Thermal Diagnostics experiments were simulated in the last LPF Simulation Campaign (November, 2013) involving all the LPF Data Analysis team and using an end-to-end simulator of the whole spacecraft. Such simulation campaign was conducted under the framework of the preparation for LPF operations.
Spanish Ministry of Science and Innovation (MICINN)/AYA2010-15709
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/407
http://www.repo.uni-hannover.de/handle/123456789/430
DOI:http://dx.doi.org/10.1088/1742-6596/610/1/012023
ISSN:1742-6588
ESSN:1742-6596
Journal of Physics Conference Series 610 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4312022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersionddc:500
Transportable setup for amplifier phase fidelity measurements
Troebs, Michael
Bogan, C.
Barke, S.
Kuehn, G.
Reiche, J.
Heinzel, Gerhard
Danzmann, Karsten
interferometer
lisa
ddc:500
ddc:530
Konferenzschrift
One possible laser source for the Laser Interferometer Space Antenna (LISA) consists of an Ytterbium-doped fiber amplifier originally developed for inter-satellite communication, seeded by the laser used for the technology demonstrator mission LISA Pathfinder. LISA needs to transmit clock information between its three spacecraft to correct for phase noise between the clocks on the individual spacecraft. For this purpose phase modulation sidebands at GHz frequencies will be imprinted on the laser beams between spacecraft. Differential phase noise between the carrier and a sideband introduced within the optical chain must be very low. We report on a transportable setup to measure the phase fidelity of optical amplifiers.
DFG/EXC/QUEST
DLR/50OQ1301
DLR/50OQ0601
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/408
http://www.repo.uni-hannover.de/handle/123456789/431
DOI:http://dx.doi.org/10.1088/1742-6596/610/1/012041
ISSN:1742-6588
ESSN:1742-6596
Journal of Physics Conference Series 610 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4322022-12-02T15:15:03Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersionddc:500
A brief comparison of optical pathlength difference and various definitions for the interferometric phase
Wanner, Gudrun
Schuster, Sönke
Tröbs, Michael
Heinzel, Gerhard
Astronomy
Astrophysics
Physics, Applied
ddc:500
ddc:530
Konferenzschrift
To this paper we discuss that the phase readout in low noise laser interferometers can significantly deviate from the underlying optical pathlength difference (OPD). The cross coupling of beam tilt to the interferometric phase readout is compared to the OPD. For such a system it is shown that the amount of tilt to phase readout coupling depends strongly on the involved beams and their parameters, as well as on the detector properties and the precise definition of the phase. The unique single element photodiode phase is therefore compared to three common phase definitions for quadrant diodes. It is shown that neither phase definition globally shows the least amount of cross coupling of angular it
Deutsches Zentrum für Luft- und Raumfahrt (DLR)/No 50 OQ 1301
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2015
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/409
http://www.repo.uni-hannover.de/handle/123456789/432
DOI:http://dx.doi.org/10.1088/1742-6596/610/1/012043
ISSN:1742-6588
ESSN:1742-6596
Journal of Physics Conference Series 610 (2015)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4392022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Magnetoresistance in a High Mobility Two-Dimensional Electron System as a Function of Sample Geometry
Bockhorn, L.
Hodaei, A.
Schuh, Dieter
Wegscheider, Werner
Haug, Rolf J.
Physics, Multidisciplinary
Physics, Condensed Matter
ddc:530
Konferenzschrift
In a high mobility two-dimensional electron gas (2DEG) realized in a GaAs/Al0.3Ga0.7As quantum well we observe changes in the Shubnikov-de Haas oscillations (SdHO) and in the Hall resistance for different sample geometries. We observe for each sample geometry a strong negative magnetoresistance around zero magnetic field which consists of a peak around zero magnetic field and of a huge magnetoresistance at larger fields. The peak around zero magnetic field is left unchanged for different geometries.
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2013
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/416
http://www.repo.uni-hannover.de/handle/123456789/439
DOI:http://dx.doi.org/10.1088/1742-6596/456/1/012003
ISSN:1742-6588
ESSN:1742-6596
Journal of Physics Conference Series 456 (2013)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4402022-12-02T15:15:01Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Exchange interaction in chirally coupled quantum dots
Tutuc, Daniel
Heine, Alexander W.
Schuh, Dieter
Wegscheider, Werner
Haug, Rolf J.
single-electron transistor
oxidation
system
Physics, Multidisciplinary
Physics, Condensed Matter
ddc:530
Konferenzschrift
We present transport measurements on a system of two lateral quantum dots in a perpendicular magnetic field. Due to edge channel formation in an open conducting region, the quantum dots are chirally coupled. When both quantum dots are tuned into the Kondo regime simultaneously, we observe a change in the temperature dependence of the differential conductance. This is explained by the RKKY exchange interaction between the two dots. As a function of bias the differential conductance shows a splitting of the Kondo resonance which changes in the presence of RKKY interaction.
DFG/EXC/QUEST
NTH School for Contacts in Nanosystems
status-type:publishedVersion
Bristol : IOP Publishing Ltd.
2013
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/417
http://www.repo.uni-hannover.de/handle/123456789/440
DOI:http://dx.doi.org/10.1088/1742-6596/456/1/012014
ISSN:1742-6588
ESSN:1742-6596
Journal of Physics Conference Series 456 (2013)
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/de/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4662022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Interaction-free measurements by quantum Zeno stabilization of ultracold atoms
Peise, Jan
Lücke, Bernd
Pezze, L.
Deuretzbacher, Frank
Ertmer, Wolfgang
Arlt, Jan J.
Smerzi, A.
Santos, Luis
Klempt, Carsten
interrogation
decay
ddc:530
Quantum mechanics predicts that our physical reality is influenced by events that can potentially happen but factually do not occur. Interaction-free measurements (IFMs) exploit this counterintuitive influence to detect the presence of an object without requiring any interaction with it. Here we propose and realize an IFM concept based on an unstable many-particle system. In our experiments, we employ an ultracold gas in an unstable spin configuration, which can undergo a rapid decay. The object-realized by a laser beam-prevents this decay because of the indirect quantum Zeno effect and thus, its presence can be detected without interacting with a single atom. Contrary to existing proposals, our IFM does not require single-particle sources and is only weakly affected by losses and decoherence. We demonstrate confidence levels of 90%, well beyond previous optical experiments.
QUEST
DFG/Research Training Group/1729
DFG/SA1031/7-1
Danish Council for Independent Research
Lundbeck Foundation
EU/EURAMET/European Metrology Research Programme (EMRP)
status-type:publishedVersion
London : Nature Publishing Group
2015-04
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/443
http://www.repo.uni-hannover.de/handle/123456789/466
DOI:http://dx.doi.org/10.1038/ncomms7811
ISSN:2041-1723
Nature Communications 6 (2015)
eng
CC BY 4.0 Unported
https://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4712022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Plutonium release from Fukushima Daiichi fosters the need for more detailed investigations
Schneider, Stephanie
Walther, Clemens
Bister, Stefan
Schauer, Viktoria
Christl, Marcus
Synal, Hans-Arno
Shozugawa, Katsumi
Steinhauser, Georg
power-plant accident
nuclear accident
japanese soils
ams facility
isotopes
pu
identification
radionuclides
contamination
environment
ddc:530
The contamination of Japan after the Fukushima accident has been investigated mainly for volatile fission products, but only sparsely for actinides such as plutonium. Only small releases of actinides were estimated in Fukushima. Plutonium is still omnipresent in the environment from previous atmospheric nuclear weapons tests. We investigated soil and plants sampled at different hot spots in Japan, searching for reactor-borne plutonium using its isotopic ratio Pu-240/Pu-239. By using accelerator mass spectrometry, we clearly demonstrated the release of Pu from the Fukushima Daiichi power plant: While most samples contained only the radionuclide signature of fallout plutonium, there is at least one vegetation sample whose isotope ratio (0.381 +/- 0.046) evidences that the Pu originates from a nuclear reactor (Pu239+240 activity concentration 0.49 Bq/kg). Plutonium content and isotope ratios differ considerably even for very close sampling locations, e.g. the soil and the plants growing on it. This strong localization indicates a particulate Pu release, which is of high radiological risk if incorporated.
CDC NIOSH Mountain and Plains Education and Research Center/T42OH009229-07
NRC/NRC-HQ-12-G-38-0044
CDC NIOSH Mountain and Plains Education and Research Center/T42OH009229-07
NRC/NRC-HQ-12-G-38-0044
status-type:publishedVersion
Lausanne : Frontiers Research Foundation
2013-10-18
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/448
http://www.repo.uni-hannover.de/handle/123456789/471
DOI:http://dx.doi.org/10.1038/srep02988
ISSN:2045-2322
Scientific Reports 3 (2013)
eng
CC BY-NC-ND 3.0 Unported
http://creativecommons.org/licenses/by-nc-nd/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4742022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Absorption Measurements of Periodically Poled Potassium Titanyl Phosphate (PPKTP) at 775 nm and 1550 nm
Steinlechner, Jessica
Ast, Stefan
Krueger, Christoph
Singh, Amrit Pal
Eberle, Tobias
Haendchen, Vitus
Schnabel, Roman
ppktp
absorption
photo-thermal
self-phase-modulation
index
light
db
ddc:530
The efficient generation of second-harmonic light and squeezed light requires non-linear crystals that have low absorption at the fundamental and harmonic wavelengths. In this work the photo-thermal self-phase modulation technique is exploited to measure the absorption coefficient of periodically poled potassium titanyl phosphate (PPKTP) at 1,550 nm and 775 nm. The measurement results are (84 +/- 40) ppm/cm and (127 +/- 24) ppm/cm, respectively. We conclude that the performance of state-of-the-art frequency doubling and squeezed light generation in PPKTP is not limited by absorption.
International Max Planck Research School (IMPRS) on Gravitational Wave Astronomy
QUEST
DFG/SFB/Transregio 7
QUEST
IMPRS
DFG/SFB/Transregio 7
status-type:publishedVersion
Basel : Mdpi Ag
2013-01
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/451
http://www.repo.uni-hannover.de/handle/123456789/474
DOI:http://dx.doi.org/10.3390/s130100565
ISSN:1424-8220
Sensors 13 (2013), Nr. 1
eng
CC BY 3.0 Unported
https://creativecommons.org/licenses/by/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4752022-12-02T15:12:32Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Characterization of nanoparticle mediated laser transfection by femtosecond laser pulses for applications in molecular medicine
Schomaker, Markus
Heinemann, Dag
Kalies, Stefan
Willenbrock, Saskia
Wagner, Siegfried
Nolte, Ingo
Ripken, Tammo
Escobar, Hugo Murua
Meyer, Heiko
Heisterkamp, Alexander
laser transfection
plasmonics
nanoparticles
permeabilization mechanisms
sirna
gene delivery
gold nanoparticles
selective nanophotothermolysis
plasmonic nanobubbles
mammalian-cells
gene-transfer
cancer
optoporation
nanomanipulations
manipulation
therapy
ddc:530
Background: In molecular medicine, the manipulation of cells is prerequisite to evaluate genes as therapeutic targets or to transfect cells to develop cell therapeutic strategies. To achieve these purposes it is essential that given transfection techniques are capable of handling high cell numbers in reasonable time spans. To fulfill this demand, an alternative nanoparticle mediated laser transfection method is presented herein. The fs-laser excitation of cell-adhered gold nanoparticles evokes localized membrane permeabilization and enables an inflow of extracellular molecules into cells. Results: The parameters for an efficient and gentle cell manipulation are evaluated in detail. Efficiencies of 90% with a cell viability of 93% were achieved for siRNA transfection. The proof for a molecular medical approach is demonstrated by highly efficient knock down of the oncogene HMGA2 in a rapidly proliferating prostate carcinoma in vitro model using siRNA. Additionally, investigations concerning the initial perforation mechanism are conducted. Next to theoretical simulations, the laser induced effects are experimentally investigated by spectrometric and microscopic analysis. The results indicate that near field effects are the initial mechanism of membrane permeabilization. Conclusion: This methodical approach combined with an automated setup, allows a high throughput targeting of several 100,000 cells within seconds, providing an excellent tool for in vitro applications in molecular medicine. NIR fs lasers are characterized by specific advantages when compared to lasers employing longer (ps/ns) pulses in the visible regime. The NIR fs pulses generate low thermal impact while allowing high penetration depths into tissue. Therefore fs lasers could be used for prospective in vivo applications.
DFG/SFB/Transregio 37
DFG/EXC/REBIRTH
DFG/Transregio 37
DFG/EXC/REBIRTH
status-type:publishedVersion
London : Biomed Central Ltd
2015-02-03
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/452
http://www.repo.uni-hannover.de/handle/123456789/475
DOI:http://dx.doi.org/10.1186/s12951-014-0057-1
ISSN:1477-3155
Journal of Nanobiotechnology 13 (2015)
eng
CC BY 4.0 Unported
https://creativecommons.org/licenses/by/4.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4802022-12-02T15:15:02Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Measurement of finite-frequency current statistics in a single-electron transistor
Ubbelohde, Niels
Fricke, Christian
Flindt, Christian
Hohls, Frank
Haug, Rolf J.
real-time detection
shot-noise
quantum
conductors
transport
ddc:530
Electron transport in nanoscale structures is strongly influenced by the Coulomb interaction that gives rise to correlations in the stream of charges and leaves clear fingerprints in the fluctuations of the electrical current. A complete understanding of the underlying physical processes requires measurements of the electrical fluctuations on all time and frequency scales, but experiments have so far been restricted to fixed frequency ranges, as broadband detection of current fluctuations is an inherently difficult experimental procedure. Here we demonstrate that the electrical fluctuations in a single-electron transistor can be accurately measured on all relevant frequencies using a nearby quantum point contact for on-chip real-time detection of the current pulses in the single-electron device. We have directly measured the frequency-dependent current statistics and, hereby, fully characterized the fundamental tunnelling processes in the single-electron transistor. Our experiment paves the way for future investigations of interaction and coherence-induced correlation effects in quantum transport.
BMBF/nanoQUIT
DFG/QUEST
Villum Kann Rasmussen Foundation
Swiss NSF
status-type:publishedVersion
Lausanne : Frontiers Research Foundation
2012-01
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/457
http://www.repo.uni-hannover.de/handle/123456789/480
DOI:http://dx.doi.org/10.1038/ncomms1620
ISSN:2041-1723
Nature Communications 3 (2012)
eng
CC BY-NC-SA 3.0 Unported
http://creativecommons.org/licenses/by-nc-sa/3.0/
frei zugänglich
oai:www.repo.uni-hannover.de:123456789/4892022-12-02T15:17:14Zcom_123456789_1col_123456789_7doc-type:Articledoc-type:Textopen_accessddc:530status-type:publishedVersion
Strong quantum memory at resonant Fermi edges revealed by shot noise
Ubbelohde, Niels
Roszak, K.
Hohls, Frank
Maire, N.
Haug, Rolf J.
Novotny, T.
singularities
metals
dynamics
ddc:530
Studies of non-equilibrium current fluctuations enable assessing correlations involved in quantum transport through nanoscale conductors. They provide additional information to the mean current on charge statistics and the presence of coherence, dissipation, disorder, or entanglement. Shot noise, being a temporal integral of the current autocorrelation function, reveals dynamical information. In particular, it detects presence of non-Markovian dynamics, i.e., memory, within open systems, which has been subject of many current theoretical studies. We report on low-temperature shot noise measurements of electronic transport through InAs quantum dots in the Fermi-edge singularity regime and show that it exhibits strong memory effects caused by quantum correlations between the dot and fermionic reservoirs. Our work, apart from addressing noise in archetypical strongly correlated system of prime interest, discloses generic quantum dynamical mechanism occurring at interacting resonant Fermi edges.
QUEST
Czech Science Foundation/204/11/J042
Foundation for Polish Science/TEAM
status-type:publishedVersion
London : Nature Publishing Group
2012-04-23
doc-type:Article
doc-type:Text
http://dx.doi.org/10.15488/466
http://www.repo.uni-hannover.de/handle/123456789/489
DOI:http://dx.doi.org/10.1038/srep00374
ISSN:2045-2322
Scientific Reports 2 (2012)
eng
CC BY-NC-SA 3.0 Unported
http://creativecommons.org/licenses/by-nc-sa/3.0/
frei zugänglich
oai_dc///col_123456789_7/100