Neutron stars with crossover to color superconducting quark matter

TL;DR

This paper explores how the phase transition in QCD, from hadronic matter to quark matter, can be constrained by neutron star observations, emphasizing the importance of color superconductivity in dense quark matter.

Contribution

It demonstrates that constraining the QCD phase diagram using neutron star data depends critically on the assumption of color superconductivity in cold dense quark matter.

Findings

Color superconductivity significantly influences neutron star phenomenology.

The switch function parameter $$ can be constrained by massive pulsar data.

The QCD phase transition modeling is sensitive to the state of dense quark matter.

Abstract

We follow the idea that the QCD phase diagram may be described by a crossover from a hadron resonance gas to perturbative QCD using the switch function ansatz of Albright, Kapusta and Young [1]. While the switch function could be calibrated at vanishing baryon chemical potential with data from lattice QCD simulations, it has been suggested recently by Kapusta and Welle [2] that in the zero temperature limit, the switch function parameter $\mu_0$ could be constrained by neutron star phenomenology, in particular by massive pulsars like PSR J0740+6620 with a mass exceeding $2~M_\odot$. In this work we demonstrate that this procedure to constrain the QCD phase diagram does crucially depend on the fact that cold dense quark matter is very likely in a color superconducting state.