Exact results for the sigma(z) two-point function of the XXZ chain Delta=1/2
Résumé
We propose a new multiple-integral representation for the correlation function [sigma(1)(z)sigma(m+1)(z)] of the XXZ spin-1/2 Heisenberg chain in the disordered regime. We show that for Delta = 1/2 the integrals can be separated and computed exactly. As an example we give the explicit results up to the lattice distance m = 8. It turns out that the answer is given as integer numbers divided by 2((m+1)2).