Quench dynamics of the Ising field theory in a magnetic field

TL;DR

This paper uses numerical simulations to study the non-equilibrium dynamics of the Ising field theory after quantum quenches, comparing results with analytic form factor predictions and exploring initial state properties.

Contribution

It provides the first detailed numerical analysis of quenches in the E8 integrable model, clarifies the validity of form factor expansions, and investigates the structure of quench overlaps.

Findings

Initial state is not of the integrable pair form.

High-energy asymptotics of overlaps differ from sinh/sine-Gordon models.

Results suggest directions for improving analytic predictions.

Abstract

We numerically simulate the time evolution of the Ising field theory after quenches starting from the $E_8$ integrable model using the Truncated Conformal Space Approach. The results are compared with two different analytic predictions based on form factor expansions in the pre-quench and post-quench basis, respectively. Our results clarify the domain of validity of these expansions and suggest directions for further improvement. We show for quenches in the $E_8$ model that the initial state is not of the integrable pair state form. We also construct quench overlap functions and show that their high-energy asymptotics are markedly different from those constructed before in the sinh/sine-Gordon theory, and argue that this is related to properties of the ultraviolet fixed point.