Tachyonic quench in a free bosonic field theory

TL;DR

This paper analyzes a bosonic field theory with a tachyonic Hamiltonian, revealing unique dynamical features such as exponential divergences and non-equilibration of low-frequency modes, with implications for quantum correlations.

Contribution

It characterizes the dynamics of a free bosonic field theory with a tachyonic Hamiltonian, highlighting its distinctive causal and entanglement properties post-quench.

Findings

Causal structure resembles a critical quench.

Physical quantities show exponential divergences.

Low-frequency modes do not equilibrate.

Abstract

We present a characterization of a bosonic field theory driven by a free (Gaussian) tachyonic Hamiltonian. This regime is obtained from a theory describing two coupled bosonic fields after a regular quench. Relevant physical quantities such as simple correlators, entanglement entropies, and the mutual information of disconnected subregions are computed. We show that the causal structure resembles a critical (massless) quench. For short times, physical quantities also resemble critical quenches. However, exponential divergences end up dominating the dynamics in a very characteristic way. This is related to the fact that the low-frequency modes do not equilibrate. Some applications and extensions are outlined.