ar X iv : c on d - m at / 9 60 31 62 v 1 2 6 M ar 1 99 6 Symmetrized DMRG Method for Excited States of Hubbard Models

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 20 54 v 1 9 F eb 1 99 6 Phase Separation in the Hubbard Model

Making use of symmetry properties and known exact results for the Hubbard Model on bipartite lattice, we show that (1) there is no phase separation for repulsive coupling at low dopings, (2) phase separation and superconductivity co-exist in the ground states for attractive coupling in a range of filling fractions.

ar X iv : c on d - m at / 9 60 31 71 v 1 2 7 M ar 1 99 6 Effect of noise for two interacting particles in a random potential

We investigated the effect of noise on propagation of two interacting particles pairs in a quasi one–dimensional random potential. It is shown that pair diffusion is strongly enhanced by short range interaction comparing with the non–interacting case.

ar X iv : c on d - m at / 9 60 31 20 v 1 1 6 M ar 1 99 6 Transport in Sand Piles , Interface Depinning , and Earthquake Models

Recent numerical results for a model describing dispersive transport in rice piles are explained by mapping the model to the depinning transition of an interface that is dragged at one end through a random medium. The average velocity of transport vanishes with system size L as < v >∼ L2−D ∼ L−0.23, and the avalanche size distribution exponent τ = 2 − 1/D ≃ 1.55, where D ≃ 2.23 from interface d...

ar X iv : c on d - m at / 9 60 31 41 v 1 2 1 M ar 1 99 6 March 1996 A remark on off - diagonal long - range order

In this work, we study some general property of a strongly correlated electron system defined on a lattice. Assuming that the lattice system exhibits off-diagonal long-range order, we show rigorously that this assumption would lead to Meissner effect. This generalizes previous results of continuous case to a lattice electron system.