Short-distance thermal correlations in the XXZ chain

Abstract

Recent studies have revealed much of the mathematical structure of the static correlationfunctions of the XXZ chain. Here we use the results of those studies in order to work outexplicit examples of short-distance correlation functions in the infinite chain. We computetwo-point functions ranging over two, three and four lattice sites as functions of thetemperature and the magnetic field for various anisotropies in the massless regime−1<Δ<1. It turns out that the new formulae are numerically efficient and allow us to obtainthe correlation functions over the full parameter range with arbitrary precision.