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Enhancement of the photon emission rate near the QCD critical point

Yukinao Akamatsu1,*, Masayuki Asakawa1,†, Masaru Hongo2,3,‡, Mikhail Stephanov4,5,§, and Ho-Ung Yee4,5,∥

  • *Contact author: yukinao.a.phys@gmail.com
  • †Contact author: yuki@phys.sci.osaka-u.ac.jp
  • ‡Contact author: hongo@phys.sc.niigata-u.ac.jp
  • §Contact author: misha@uic.edu
  • ∥Contact author: hyee@uic.edu
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Phys. Rev. D 113, 034009 – Published 5 February, 2026

DOI: https://doi.org/10.1103/d6nz-ctrc

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 similar to conductivity, increasing with the correlation length (ξ), diverging at the critical point. The spectrum exhibits ωdNγ/d3k∝ω−1/2 in the scaling regime, with the transition occurring at a frequency comparable to shear damping rate ω∼γη/ξ2, reflecting the nonequilibrium properties of the near-critical liquid.

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Phys. Rev. D 113, 034009– Published 5 February, 2026
  • Received 18 June 2025
  • Accepted 7 January 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.

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