Matter And Gravitation In Collisions of heavy ions and neutron stars: equation of state

TL;DR

This paper explores how gravitational waves from neutron star mergers and heavy ion collision experiments can jointly inform us about the equation of state of dense QCD matter, revealing phase structures at high density and temperature.

Contribution

It demonstrates a unified approach to modeling the equation of state applicable to both neutron star physics and laboratory heavy ion collisions.

Findings

Gravitational wave signals are sensitive to the quark matter phase.

Heavy ion collision data at high densities match neutron star core conditions within 20%.

A unified equation of state can be used for astrophysics and laboratory experiments.

Abstract

The gravitational waves emitted from a binary neutron star merger, as predicted from general relativistic magneto-hydrodynamics calculations, are sensitive to the appearance of quark matter and the stiffness of the equation of state of QCD matter present in the inner cores of the stars. This is a new messenger observable from outer space, which does provide direct signals for the phase structure of strongly interacting QCD matter at high baryon density and high temperature. These astrophysically created extremes of thermodynamics do match, to within 20\%, the values of densities and temperatures which we find in relativistic hydrodynamics and transport theory of heavy ion collisions at the existing laboratories, if though at quite different rapidity windows, impact parameters and bombarding energies of the heavy nuclear systems. We demonstrate how one unified equation of state can be constructed and used for both neutron star physics and hot QCD matter excited at laboratory facilities. The similarity in underlying QCD physics allows the gravitational wave signals from future advanced LIGO and Virgo events to be combined with the analysis of high multiplicity fluctuations and flow measurements in heavy ion detectors in the lab to pin down the EoS and the phase structure of dense matter.