• Numerical Methods for Variational Phase-Field Fracture Problems 

  Mang, Katrin; Wick, Thomas (Hannover : Institutionelles Repositorium der Leibniz Universität Hannover, 2019-07-19)

  In these lectures notes, the variational phase-field approach for modeling fracture propagation is edited for the usage in classes and summer schools. Basic modeling is briefly reviewed first. The main emphasis is on the ...
• Twisting the N=2 string 

  Ketov, Sergei V.; Lechtenfeld, Olaf; Parkes, Andrew J. (College Park (Maryland) : American Physical Society, 1995)

  The most general homogeneous monodromy conditions in N=2 string theory are classified in terms of the conjugacy classes of the global symmetry group U(1,1)⊗openZ2. For classes which generate a discrete subgroup Γ, the ...
• On the N=2 supersymmetric Camassa-Holm and Hunter-Saxton equations 

  Lenells, Jonatan; Lechtenfeld, Olaf (College Park (Maryland) : American Institute of Physics, 2009)

  We consider N=2 supersymmetric extensions of the Camassa–Holm and Hunter-Saxton equations. We show that they admit geometric interpretations as Euler equations on the superconformal algebra of contact vector fields on the ...
• Superfield formulation of nonlinear N=4 supermultiplets 

  Bellucci, Stefano; Krivonos, Sergey; Lechtenfeld, Olaf; Shcherbakov, Andrey (College Park (Maryland) : American Physical Society, 2008)

  We propose a unified superfield formulation of N=4 off-shell supermultiplets in one spacetime dimension using the standard N=4 superspace. The main idea of our approach is a gluing together of two linear supermultiplets ...
• Target duality in N=8 superconformal mechanics and the coupling of dual pairs 

  Gonzales, Marcelo; Khodaee, Sadi; Lechtenfeld, Olaf; Toppan, Francesco (College Park (Maryland) : American Institute of Physics, 2013)

  We couple dual pairs of N=8 superconformal mechanics with conical targets of dimension d and 8−d. The superconformal coupling generates an oscillator-type potential on each of the two target factors, with a frequency ...
• Supersymmetric Calogero models by gauging 

  Fedoruk, Sergey; Ivanov, Evgeny; Lechtenfeld, Olaf (College Park (Maryland) : American Physical Society, 2009)

  New superconformal extensions of d=1 Calogero-type systems are obtained by gauging the U(n) isometry of matrix superfield models. We consider the cases of N=1, N=2, and N=4 as one-dimensional supersymmetries. The bosonic ...
• Harmonic N=2 mechanics 

  Galajinsky, Anton; Lechtenfeld, Olaf (College Park (Maryland) : American Physical Society, 2009)

  N=2 superconformal many-body quantum mechanics in arbitrary dimensions is governed by a single scalar prepotential which determines the bosonic potential and the boson-fermion couplings. We present a special class of such ...
• Chern-Simons flows on Aloff-Wallach spaces and spin(7) instantons 

  Haupt, Alexander S.; Ivanova, Tatiana A.; Lechtenfeld, Olaf; Popov, Alexander D. (College Park (Maryland) : American Physical Society, 2011)

  Because of their explicit construction, Aloff-Wallach spaces are prominent in flux compactifications. They carry G2 structures and admit the G2-instanton equations, which are natural Bogomol’nyi-Prasad-Sommerfeld equations ...
• Higher-derivative N=4 superparticle in three-dimensional spacetime 

  Kozyrev, Nikolay; Krivonos, Sergey; Lechtenfeld, Olaf; Nersessian, Armen (College Park (Maryland) : American Physical Society, 2014)

  Using the coset approach (nonlinear realization) we construct component actions for a superparticle in three-dimensional spacetime with N=4 supersymmetry partially broken to N=2. These actions may contain an anyonic term ...
• N=4 supersymmetry and the Belavin-Polyakov-Shvarts-Tyupkin instanton 

  Krivonos, Sergey; Lechtenfeld, Olaf; Sutulin, Anton (College Park (Maryland) : American Physical Society, 2010)

  In this paper we construct the Lagrangian and Hamiltonian formulations of N=4 supersymmetric systems describing the motion of an isospin particle on a conformally flat four-manifold with SO(4) isometry carrying the non-Abelian ...
• The noncommutative sine-Gordon breather 

  Fischer, André; Lechtenfeld, Olaf (College Park (Maryland) : American Institute of Physics, 2009)

  As shown by Lechtenfeld et al. [Nucl. Phys. B 705, 447 (2005)], there exists a noncommutative deformation of the sine-Gordon model which remains (classically) integrable but features a second scalar field. We employ the ...
• SU(2) reduction in N=4 supersymmetric mechanics 

  Krivonos, Sergey; Lechtenfeld, Olaf (College Park (Maryland) : American Physical Society, 2009)

  We perform an su(2) Hamiltonian reduction of the general su(2)-invariant action for a self-coupled (4, 4, 0) supermultiplet. As a result, we elegantly recover the N=4 supersymmetric mechanics with spin degrees of freedom ...
• Superintegrability of generalized Calogero models with oscillator or Coulomb potential 

  Hakobyan, Tigran; Lechtenfeld, Olaf; Nersessian, Armen (College Park (Maryland) : American Physical Society, 2014)

  We deform N-dimensional (Euclidean, spherical and hyperbolic) oscillator and Coulomb systems, replacing their angular degrees of freedom by those of a generalized rational Calogero model. Using the action-angle description, ...
• Higher-derivative superparticle in AdS3 space 

  Kozyrev, Nikolay; Krivonos, Sergey; Lechtenfeld, Olaf (College Park (Maryland) : American Physical Society, 2016)

  Employing the coset approach we construct component actions for a superparticle moving in AdS3 with N=(2,0), D=3 supersymmetry partially broken to N=2, d=1. These actions may contain higher time-derivative terms, which are ...
• Spherical Calogero model with oscillator/Coulomb potential: Classical case 

  Correa, Francisco; Hakobyan, Tigran; Lechtenfeld, Olaf; Nersessian, Armen (College Park (Maryland) : American Physical Society, 2016)

  We construct the Hamiltonians and symmetry generators of Calogero-oscillator and Calogero-Coulomb models on the N-dimensional sphere within the matrix-model reduction approach. Our method also produces the integrable ...
• Post-Newtonian corrections to Schrödinger equations in gravitational fields 

  Schwartz, Philip K.; Giulini, Domenico (Bristol : IOP Publishing Ltd., 2019)

  In this paper we extend the WKB-like 'non-relativistic' expansion of the minimally coupled Klein-Gordon equation after (Kiefer and Singh 1991 Phys. Rev. D 44 1067-76; Lammerzahl 1995 Phys. Lett. A 203 12-7; Giulini and ...
• Stochastic formulation of energy level statistics 

  Hasegawa, H.; Mikeska, H.J.; Frahm, Holger (College Park (Maryland) : American Physical Society, 1988)

  It is shown that the joint distribution of energy eigenvalues for systems with a varying degree of nonintegrability which has been obtained dynamically by T. Yukawa [Phys. Rev. Lett. 54, 1883 (1985)] can also be deduced ...
• Quantum suppression of irregularity in the spectral properties of the kicked rotator 

  Frahm, Holger; Mikeska, H.J. (College Park (Maryland) : American Physical Society, 1988)

  The statistical properties of the quasienergy spectrum are used to measure the influence of quantum effects on the quantum kicked rotator which displays chaotic behavior in the classical limit. A transition from ...
• Frahm and Mikeska reply 

  Frahm, Holger; Mikeska, H.J. (College Park (Maryland) : American Physical Society, 1988)

  [no abstract available]
• Critical exponents for the one-dimensional Hubbard model 

  Frahm, Holger; Korepin, V.E. (College Park (Maryland) : American Physical Society, 1990)

  Using results on the scaling of energies with the size of the system and the principles of conformal quantum field theory, we calculate the asymptotics of correlation functions for the one-dimensional Hubbard model in the ...

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