ar X iv : c on d - m at / 0 30 71 42 v 1 7 J ul 2 00 3 Bound state of dimers on a spherical surface

ar X iv : c on d - m at / 0 30 71 02 v 1 4 J ul 2 00 3 Electronic and magnetic properties of GaMnAs : Annealing effects

The effect of short-time and long-time annealing at 250 • C on the conductivity, hole density, and Curie temperature of GaMnAs single layers and GaMnAs/InGaMnAs heterostructures is studied by in-situ conductivity measurements as well as Raman and SQUID measurements before and after annealing. Whereas the conductivity monotonously increases with increasing annealing time, the hole density and th...

ar X iv : c on d - m at / 0 30 74 20 17 J ul 2 00 3 Non - Fermi liquid normal state of the Heavy Fermion superconductor UBe 13

ar X iv : m at h - ph / 0 30 70 15 v 1 8 J ul 2 00 3 Integrable geodesic flows on Riemannian manifolds : Construction and Obstructions ∗ Alexey

This paper is a review of recent and classical results on integrable geodesic flows on Riemannian manifolds and topological obstructions to integrability. We also discuss some open problems.

ar X iv : 0 80 7 . 00 58 v 1 [ m at h . D G ] 1 J ul 2 00 8 EQUIVARIANT DIFFERENTIAL CHARACTERS AND SYMPLECTIC REDUCTION

We describe equivariant differential characters (classifying equi-variant circle bundles with connections), their prequantization, and reduction.

ar X iv : 0 71 2 . 28 10 v 1 [ m at h - ph ] 1 7 D ec 2 00 7 Ground state energy of the low density Hubbard model

We derive a lower bound on the ground state energy of the Hubbard model for given value of the total spin. In combination with the upper bound derived previously by Giuliani [3], our result proves that in the low density limit, the leading order correction compared to the ground state energy of a non-interacting lattice Fermi gas is given by 8πa̺u̺d, where ̺u(d) denotes the density of the spin-up ...