Quasinormal modes of nonthermal fixed points

TL;DR

This paper introduces a new class of quasinormal modes that describe how nonthermal fixed points evolve towards equilibrium across various physical systems, using black hole perturbation techniques.

Contribution

It identifies and computes the spectrum of these novel quasinormal modes for a kinetic theory with a Focker-Planck collision kernel, linking them to nonthermal fixed points.

Findings

Quasinormal modes form a tower of decaying power-law contributions.

Improved understanding of the distribution function at nonthermal fixed points.

Application of black hole perturbation theory to non-equilibrium kinetic systems.

Abstract

Quasinormal modes play a prominent role in relaxation of diverse physical systems to equilibria, ranging from astrophysical black holes to tiny droplets of quark-gluon plasma at RHIC and LHC accelerators. We propose that a novel kind of quasinormal modes govern the direct approach to self-similar time evolution of nonthermal fixed points, whose relevance ranges from high energy physics to cold atom gases. We utilize black hole perturbation theory techniques to compute the spectrum of these far from equilibrium quasinormal modes for a kinetic theory with a Focker-Planck collision kernel in isotropic and homogeneous states. Our conclusion is that quasinormal modes of nonthermal fixed points give rise to a tower of progressively more decaying power-law contributions. A byproduct of our analysis is a precise determination and improved understanding of the distribution function characterizing nonthermal fixed points.