Numerical and Monte Carlo Bethe ansatz method: 1D Heisenberg model

In this paper we present two new numerical methods for studying thermodynamic quantities of integrable models. As an example of the effectiveness of these two approaches, results from numerical solutions of all sets of Bethe ansatz equations, for small Heisenberg chains, and Monte Carlo simulations in quasi-momentum space, for a relatively larger chains, are presented. Our results agree with those obtained by the thermodynamic Bethe ansatz (TBA). As an application of these ideas, the pairwise entanglement between two nearest neighbors at finite temperatures is studied. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005