Entropy Production, Hydrodynamics, and Resurgence in the Primordial Quark-Gluon Plasma from Holography

TL;DR

This paper uses holography to analyze the non-equilibrium entropy production of the primordial quark-gluon plasma in an expanding universe, revealing divergence in series expansions and the importance of resummation for accurate predictions.

Contribution

It develops a holographic framework to study entropy production in a non-conformal plasma during cosmic expansion, including the resurgent properties of the series expansion.

Findings

Series expansion for entropy production has zero radius of convergence.

Resummation significantly alters the estimated entropy production rate.

Bulk viscosity approximation can be inaccurate depending on parameters.

Abstract

Microseconds after the Big Bang quarks and gluons formed a strongly-coupled non-conformal liquid driven out-of-equilibrium by the expansion of the Universe. We use holography to determine the non-equilibrium behavior of this liquid in a Friedmann-Lemaitre-Robertson-Walker Universe and develop an expansion for the corresponding entropy production in terms of the derivatives of the cosmological scale factor. We show that the resulting series has zero radius of convergence and we discuss its resurgent properties. Finally, we compute the resummed entropy production rate in de Sitter Universe at late times and show that the leading order approximation given by bulk viscosity effects can strongly overestimate/underestimate the rate depending on the microscopic parameters.