Low-temperature asymptotics for the transverse dynamical structure factor for a magnetically polarized $XX$ chain at small and negative frequencies

TL;DR

This paper derives accurate low-temperature asymptotics for the transverse dynamical structure factor of a magnetically polarized $XX$ chain at small and negative frequencies, avoiding previous limitations by not relying on magnetic susceptibility representation.

Contribution

It introduces a method to compute the structure factor's asymptotics without using magnetic susceptibility, improving accuracy at small and negative frequencies.

Findings

Correct low-temperature asymptotics at small frequencies

Valid results at negative frequencies

Enhanced understanding of $XX$ chain dynamics

Abstract

Using the truncated form factor expansion the low-temperature asymptotics for the transverse dynamical structure factor of the magnetically polarized $XX$ chain is studied. Unlike the previous paper we do not use the representation of structure factor in terms of the corresponding magnetic susceptibility. This enables to obtain correct results at small and negative frequencies.