Electromagnetic signal of the QCD phase transition in neutron star mergers

TL;DR

This paper explores the electromagnetic signals, specifically photon production, from neutron star mergers as a probe of the QCD phase transition to quark matter, highlighting potential cooling effects and phase diagram insights.

Contribution

It introduces a novel approach to detect the QCD phase transition in neutron star mergers through electromagnetic signals caused by the conformal anomaly.

Findings

Photon production is sensitive to the QCD phase transition.

Photon radiation affects the cooling and energy loss in mergers.

Potential observational signatures of quark matter formation.

Abstract

Mergers of binary neutron stars create conditions of supranuclear density $n\gtrsim n_{\rm nuc}\simeq 0.17 {\rm fm}^{-3}$ and moderate temperature $50\lesssim T \lesssim 90 {\rm MeV}$. These events thus probe a sensitive region of the density-temperature phase diagram of QCD matter. We study photon production by the QCD conformal anomaly for a signal of a possible transition to quark degrees of freedom during the merger. We discuss energy loss due to photon radiation as a cooling mechanism that is sensitive to the bulk viscosity and thermal conductivity of the quark matter.