Spontaneous Symmetry Breaking, Spectral Statistics, and the Ramp

TL;DR

This paper explores how spontaneous symmetry breaking in quantum chaotic systems affects spectral statistics, revealing an unexpected enhancement of the spectral form factor across various symmetry breaking patterns.

Contribution

It extends existing spectral statistics analysis to include spontaneous symmetry breaking, providing formulas for enhancement effects in diverse symmetry scenarios.

Findings

Spontaneous symmetry breaking enhances the spectral form factor.

Formulas derived for $Z_n$, $U(1)$, and non-Abelian symmetry breaking.

Results apply to both toy models and hydrodynamic models.

Abstract

Ensembles of quantum chaotic systems are expected to exhibit energy eigenvalues with random-matrix-like level repulsion between pairs of energies separated by less than the inverse Thouless time. Recent research has shown that exact and approximate global symmetries of a system have clear signatures in these spectral statistics, enhancing the spectral form factor or correspondingly weakening level repulsion. This paper extends those results to the case of spontaneous symmetry breaking, and shows that, surprisingly, spontaneously breaking a symmetry further enhances the spectral form factor. For both RMT-inspired toy models and models where the symmetry breaking has a description in terms of fluctuating hydrodynamics, we obtain formulas for this enhancement for arbitrary symmetry breaking patterns, including $Z_n$, $U(1)$, and partially or fully broken non-Abelian symmetries.