Non-perturbative determination of the QCD Equation of State up to the electroweak scale

TL;DR

This paper non-perturbatively determines the QCD Equation of State from the electroweak scale down to 3 GeV, revealing the necessity of non-perturbative contributions even at very high temperatures.

Contribution

It introduces a novel non-perturbative approach combining shifted boundary conditions and renormalized coupling to study QCD at high temperatures.

Findings

QCD Equation of State accurately described only with non-perturbative terms at high T

Method applicable to QCD with different quark flavours

Smooth connection between high-temperature and low-temperature regimes

Abstract

The QCD Equation of State with $N_f=3$ massless quark flavours is determined non-perturbatively over a broad range of temperatures, extending from the electroweak scale down to 3 GeV, and smoothly connecting to the low-temperature regime. The comparison with perturbative predictions shows that, even at temperatures approaching the electroweak scale, the Equation of State can be accurately described only by adding terms beyond the known perturbative series, including non-perturbative contributions. The strategy that allows this investigation in the previously unexplored high-temperature regime combines shifted boundary conditions with a determination of the lines of constant physics based on the running of a non-perturbatively defined renormalized coupling. This methodology is general and can be applied to QCD with four or five massive quark flavours.