Enhancement of photon emission rate near QCD critical point

TL;DR

This paper predicts a significant enhancement in photon emission rates near the QCD critical point, using an effective theory to derive a universal spectrum that diverges at criticality, revealing nonequilibrium effects.

Contribution

It introduces a novel theoretical framework to compute photon emission near the QCD critical point, highlighting the universal scaling behavior and divergence at criticality.

Findings

Photon emission rate scales with correlation length, diverging at the critical point.

Derived a universal photon spectrum with a specific frequency dependence.

Identified the transition frequency related to shear damping rate.

Abstract

We compute photon emission rate enhancement near the QCD critical point using an effective theory of dynamic critical phenomena and derive a universal photon spectrum. The emission rate scales similarly to conductivity, increasing with the correlation length ($\xi$), diverging at the critical point. The spectrum exhibits $\omega dN_{\gamma}/d^3k \propto \omega^{-1/2}$ in the scaling regime, with the transition occurring at a frequency comparable to shear damping rate $\omega \sim \gamma_{\eta}/\xi^2$, reflecting the nonequilibrium properties of the near-critical liquid.