Quantum Quenches in Integrable Field Theories

TL;DR

This paper investigates the non-equilibrium dynamics of integrable quantum field theories after sudden parameter changes, showing that local operator expectations tend toward a generalized Gibbs ensemble with mode-dependent effective temperatures.

Contribution

It provides a method to compute long-time limits of local operators in integrable field theories post-quench using form factors, supporting the generalized Gibbs ensemble hypothesis.

Findings

Long-time local operator expectations align with a generalized Gibbs ensemble.

Different eigenmodes have distinct effective temperatures after a quench.

The approach offers a way to analyze non-equilibrium dynamics in integrable models.

Abstract

We study the non equilibrium time evolution of an integrable field theory in 1+1 dimensions after a sudden variation of a global parameter of the Hamiltonian. For a class of quenches defined in the text, we compute the long times limit of the one point function of a local operator as a series of form factors. Even if some subtleties force us to handle this result with care, there is a strong evidence that for long times the expectation value of any local operator can be described by a generalized Gibbs ensemble with a different effective temperature for each eigenmode.