Infinite-time Average of Local Fields in an Integrable Quantum Field Theory after a Quantum Quench

TL;DR

This paper presents a method to compute the long-time averages of local fields in integrable quantum field theories after a quench, using form factors and the Generalized Bethe Ansatz.

Contribution

It introduces a novel approach combining form factors and the Bethe Ansatz to evaluate infinite-time averages in integrable quantum field theories.

Findings

Method accurately predicts long-time local field averages.

Connects form factors with long-time dynamics post-quench.

Provides a framework for experimental and theoretical comparison.

Abstract

The infinite-time average of the expectation values of local fields of any interacting quantum theory after a global quench process are key quantities for matching theoretical and experimental results. For quantum integrable field theories, we show that they can be obtained by an ensemble average that employs a particular limit of the Form Factors of local fields and quantities extracted by the Generalized Bethe Ansatz.