ar X iv : c on d - m at / 9 60 20 27 v 1 6 F eb 1 99 6 Néel and singlet RVB orders in the t - J model

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 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 10 27 v 1 9 J an 1 99 6 A possible phase diagram of a t - J ladder model

We investigate a t-J ladder model by numerical diagonalization method. By calculating correlation functions and assuming the Luttinger liquid relation, we obtained a possible phase diagram of the ground state as a function of J/t and electron density n. We also found that behavior of correlation functions seems to consist with the prediction of Luttinger liquid relation. The result suggests tha...

ar X iv : h ep - p h / 96 02 20 5 v 1 1 F eb 1 99 6 Multiplicity Distributions in QCD and λφ 36 - model

ar X iv : d g - ga / 9 60 20 02 v 1 1 F eb 1 99 6 Associativity properties of the symplectic sum

In this note we apply a 4-fold sum operation to develop an associativity rule for the pairwise symplectic sum. This allows us to show that certain diffeomorphic symplectic 4-manifolds made out of elliptic surfaces are in fact symplectically deformation equivalent. We also show that blow-up points can be traded from one side of a symplectic sum to another without changing the symplectic deformat...