Quantitative analysis of the gravitational wave spectrum sourced from a first-order chiral phase transition of QCD

We investigate the cosmological first-order chiral phase transition of quantum chromodynamics (QCD), and for the first time calculate its parameters which can 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 O(102) MeV. These results further suggest that the gravitational wave (GW) signals of NANOGrav are very unlikely sourced from the chiral phase transition of QCD.