Euler equations on a semi-direct product of the diffeomorphisms group by itself

Abstract

The geodesic equations of a class of right invariant metrics on the semi-direct product Diff(S 1)sDiff(S 1) are studied. The equations are explicitly described, they have the form of a system of coupled equations of Camassa-Holm type and possess singular (peakon) solutions. Their integrability is further investigated, however no compatible bi-Hamiltonian structures on the corresponding dual Lie algebra (Vect(S 1) sVect(S 1))* are found.