Density matrix of a finite sub-chain of the Heisenberg anti-ferromagnet

TL;DR

This paper derives a compact formula for the density matrix of a finite sub-chain in the homogeneous Heisenberg anti-ferromagnet, advancing understanding of quantum correlations in this fundamental model.

Contribution

It provides a simplified, explicit expression for the density matrix in the homogeneous XXX model, extending previous inhomogeneous results.

Findings

Derived a compact formula for the density matrix

Enhanced understanding of quantum correlations in the Heisenberg model

Simplified calculations for the homogeneous case

Abstract

We consider a finite sub-chain on an interval of the infinite XXX model in the ground state. The density matrix for such a subsystem was described in our previous works for the model with inhomogeneous spectral parameters. In the present paper, we give a compact formula for the physically interesting case of the homogeneous model.