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Enhancement of axial anomaly effects in hot two-color QCD: FRG approach in the linear sigma model

Gergely Fejős1,2 and Daiki Suenaga3,4

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Phys. Rev. D 112, 114028 – Published 16 December, 2025

DOI: https://doi.org/10.1103/s79l-gkt2

Abstract

We investigate the thermal properties of hadrons in two-color quantum chromodynamics (QC2D) using the functional renormalization group method, with particular focus on modifications of the U(1) axial anomaly effects. The hadrons are described by a linear sigma model based on the Pauli-Gürsey SU(4) symmetry, which incorporates both low-lying 0± mesons and diquark baryons. We find that all quartic couplings are comparably suppressed when physical values of the pion mass and decay constant are taken as inputs, for which a reasonably smooth chiral symmetry restoration at finite temperature is reproduced. Consequently, mass differences among chiral partners remain small. Despite these tiny mass differences, mass degeneracies of chiral partners in the hot medium are clearly demonstrated, consistent with chiral symmetry restoration. Moreover, we find that the couplings responsible for the U(1) axial anomaly are enhanced upon entering the finite-temperature regime. Baryonic fluctuations also provide sizable contributions to these enhancements. Finally, the fate of the topological susceptibility in the hot QC2D medium is examined.

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Phys. Rev. D 112, 114028– Published 16 December, 2025
  • Received 25 June 2025
  • Accepted 21 November 2025
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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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