QCD Phase Diagram and Astrophysical Implications

TL;DR

This paper reviews the QCD phase diagram, the equation of state from neutron star data, and discusses astrophysical implications including gravitational wave signals and the possibility of quark matter.

Contribution

It provides a synthesis of QCD phases, neutron star matter properties, and explores the potential of gravitational waves to substantiate quark matter presence.

Findings

QCD crossover occurs at low baryon density and temperature.

Neutron star matter exhibits complex thermodynamic properties at twice nuclear saturation density.

Gravitational wave signals could help confirm quark matter in neutron stars.

Abstract

I make a brief review about the QCD phases and the equation of state inferred from the neutron star data. Along the temperature axis at low baryon density, the QCD phase transition is a smooth crossover, and it is a natural extension of our imagination to postulate a similar crossover along the density axis at low temperature. Even without phase transitions, the inferred thermodynamic properties of neutron star matter turn out to be highly nontrivial already at twice of the nuclear saturation density. I also give some discussions about the substantiation of quark matter by means of the gravitational wave signals including the multi-messenger prospect.