A quantitative analysis of Gravitational Wave spectrum sourced from First-Order Chiral Phase Transition of QCD

TL;DR

This paper analyzes the gravitational wave spectrum from the QCD chiral phase transition, finding it unlikely to explain NANOGrav signals due to the transition's weak and rapid nature at low temperatures.

Contribution

It provides the first detailed calculation of the parameters governing gravitational waves from the QCD chiral phase transition using advanced functional QCD methods.

Findings

QCD phase transition is weak and fast at low temperatures

Gravitational wave signals from this transition are unlikely to match NANOGrav observations

The study offers new quantitative insights into QCD's cosmological phase transition

Abstract

We investigate the cosmological first-order chiral phase transition of QCD, and for the first time calculate its parameters which can fully determine the gravitational wave spectrum. With the state-of-the-art calculation from the functional QCD method, we found that the large chemical potential of QCD phase transition results in very weak and fast first-order phase transitions at the temperature lower than $\mathcal{O}(10^2)$ MeV. These results further suggest that the GW signals of NANOGrav are very unlikely sourced from the chiral phase transition of QCD.