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  • Open Access

Quasinormal Modes of Nonthermal Fixed Points

Matisse De Lescluze* and Michal P. Heller†

  • *Contact author: matisse.delescluze@ugent.be
  • †Contact author: michal.p.heller@ugent.be
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Phys. Rev. Lett. 135, 091601 – Published 28 August, 2025

DOI: https://doi.org/10.1103/tz78-jfbw

Abstract

Quasinormal modes play a prominent role in the relaxation of diverse physical systems to equilibria, ranging from astrophysical black holes to tiny droplets of quark-gluon plasma at the RHIC and LHC accelerators. We propose that a novel kind of quasinormal mode governs 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 Fokker-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 by-product of our analysis is a precise determination and improved understanding of the distribution function characterizing nonthermal fixed points.

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Phys. Rev. Lett. 135, 091601– Published 28 August, 2025
  • Received 14 February 2025
  • Revised 9 May 2025
  • Accepted 18 July 2025
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