Impact of Localization in Early-Universe QCD Phase Transition

TL;DR

This paper presents a modified QCD phase transition model incorporating quark localization effects, which results in a higher critical temperature, earlier phase transition onset, and better alignment with lattice QCD data, impacting early universe cooling.

Contribution

It introduces a phenomenological model that accounts for quark localization effects in the early universe's QCD phase transition, improving agreement with lattice QCD results.

Findings

Critical temperature increased by roughly 7%

Phase transition occurs earlier, shortening the mixed phase by 24%

Model aligns better with lattice QCD data from HotQCD

Abstract

We introduce a phenomenological modification of the MIT bag model equation of state that incorporates quark localization arising from gluon-induced disorder in the quark-gluon plasma. This model effectively reduces the quark degrees of freedom encoded in the product of the disorder activation function $G(W)$ and the localization efficiency factor $H(T)$. As a result, the critical temperature is increased roughly by 7%. Employing the Friedmann equation, we find that the onset of the phase transition occurs earlier. Consequently, the mixed phase duration is only $8.22\, \mu s$, which is 24% shorter than the bag model, and the hadronic phase cools faster. The Stephan-Boltzmann constant is reached at much higher temperatures, causing the energy density and pressure curves of the bag model to shift downward and yielding better agreement with the lattice QCD data from the HotQCD collaboration. Our results show that the localization of quarks plays a significant role in the cooling dynamics of the early universe.