Integral representation of the density matrix of the XXZ chain at finite temperatures
arXiv:cond-mat/0412062 · doi:10.1088/0305-4470/38/9/001
Abstract
We present an integral formula for the density matrix of a finite segment of the infinitely long spin-1/2 XXZ chain. This formula is valid for any temperature and any longitudinal magnetic field.
12 pages, Latex