ar X iv : c on d - m at / 9 60 51 25 v 1 2 0 M ay 1 99 6

ar X iv : c on d - m at / 9 60 51 41 v 1 2 2 M ay 1 99 6 Spread width for two interacting particles in one - dimensional random potential

For two interacting particles (TIP) in one-dimensional random potential the dependence of the spread width Γ, the local density of states and the TIP localization length on system parameters is determined analytically. The theoretical predictions for Γ are confirmed by numerical simulations.

ar X iv : c on d - m at / 9 60 51 64 v 1 2 7 M ay 1 99 6 Influence of electron phonon interaction on superexchange

We investigate the influence of electron-phonon coupling on the superex-change interaction of magnetic insulators. Both the Holstein-Hubbard model where the phonons couple to the electron density, as well as an extended Su, Schrieffer, Heeger model where the coupling arises from modulation of the overlap integral are studied using exact diagonalization and perturba-tive methods. In all cases fo...

ar X iv : d g - ga / 9 51 20 10 v 2 2 4 M ay 1 99 6 Weierstrass representations for harmonic morphisms on Euclidean spaces and spheres

We construct large families of harmonic morphisms which are holomorphic with respect to Hermitian structures by finding heierarchies of Weierstrass-type representations. This enables us to find new examples of complex-valued harmonic mor-phisms from Euclidean spaces and spheres.

ar X iv : c on d - m at / 9 60 31 90 v 1 2 9 M ar 1 99 6 The Four - Dimensional XY Spin Glass

ar X iv : c on d - m at / 9 60 51 84 v 1 2 9 M ay 1 99 6 WU - JIK - 96 - 2 Electrostriction of Polar Glasses

We develop a finite temperature theory for the susceptibility and electrostriction of isotropic substances in which permanent electric dipoles are restrained from free rotation by elastic forces. All parameters are constrained by the measured susceptibility and elastic constants. When applied to polyurethane, the predicted electrostriction is approximately consistent with some of the wide range...

ar X iv : c on d - m at / 9 60 50 32 v 1 6 M ay 1 99 6 THE LOW - TEMPERATURE PHASE OF KAC - ISING MODELS

We analyse the low temperature phase of ferromagnetic Kac-Ising models in dimensions d ≥ 2. We show that if the range of interactions is γ, then two disjoint translation invariant Gibbs states exist, if the inverse temperature β satisfies β − 1 ≥ γ, where κ = d(1−ǫ) (2d+1)(d+1) , for any ǫ > 0. The prove involves the blocking procedure usual for Kac models and also a contour representation for ...