Enhancement of photon emission rate near QCD critical point

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 $\omega d{N}_{\gamma }\mathrm{/}{d}^{3}k\propto {\omega }^{-1\mathrm{/}2}$ in the scaling regime, with the transition occurring at a frequency comparable to shear damping rate $\omega \sim {\gamma }_{\eta }\mathrm{/}{\xi }^2$, reflecting the nonequilibrium properties of the near-critical liquid.