On Truncated Generalized Gibbs Ensembles in the Ising Field Theory

TL;DR

This paper compares two truncated Generalized Gibbs Ensembles in the Ising Field Theory, showing that semi-local charges provide a more accurate description of the stationary state after a mass quench.

Contribution

It introduces and tests two different truncated GGE approaches, highlighting the superior performance of semi-local charges in modeling the stationary state.

Findings

Both GGEs recover the single-particle Green's function G(x).

Semi-local charges outperform ultra-local charges for the same number of charges.

The study advances understanding of GGE truncation effectiveness in quantum quenches.

Abstract

We discuss the implementation of two different truncated Generalized Gibbs Ensembles (GGE) describing the stationary state after a mass quench process in the Ising Field Theory. One truncated GGE is based on the semi-local charges of the model, the other on regularized versions of its ultra-local charges. We test the efficiency of the two different ensembles by comparing their predictions for the stationary state values of the single-particle Green's function $G(x) = \langle \psi^{\dagger}(x) \psi(0) \rangle$ of the complex fermion field $\psi(x)$. We find that both truncated GGEs are able to recover $G(x)$, but for a given number of charges the semi-local version performs better.