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Challenges in locating the QCD critical point via constant entropy density contours

Michał Marczenko1,*, Michał Szymański2,†, and Győző Kovács2,3,‡

  • 1Incubator of Scientific Excellence - Centre for Simulations of Superdense Fluids, University of Wrocław, plac Maksa Borna 9, PL-50204 Wrocław, Poland
  • 2Institute of Theoretical Physics, University of Wrocław, plac Maksa Borna 9, PL-50204 Wrocław, Poland
  • 3Institute for Particle and Nuclear Physics, HUN-REN Wigner Research Centre for Physics, 1121 Budapest, Konkoly–Thege Miklós út 29-33, Hungary

  • *Contact author: michal.marczenko@uwr.edu.pl
  • †Contact author: michal.szymanski@uwr.edu.pl
  • ‡Contact author: gyozo.kovacs@uwr.edu.pl
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Phys. Rev. D 112, 034019 – Published 19 August, 2025

DOI: https://doi.org/10.1103/nwn6-4m4g

Abstract

A new method was proposed recently to investigate the location of the putative critical point of strongly interacting matter, governed by quantum chromodynamics. By approximating contours of constant entropy density at finite baryon chemical potential, the conditions for the existence of a critical point are solved. In this work, we analyze this method in the hadron resonance gas and Nambu–Jona-Lasinio models. We demonstrate that the prediction of the critical point in the HRG model is solely due to mesonic and baryonic degrees of freedom, and thus is not necessarily a signal of a critical point. We argue that such an expansion leads to a physically meaningful prediction only when applied near the critical point.

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Phys. Rev. D 112, 034019– Published 19 August, 2025
  • Received 13 May 2025
  • Accepted 5 August 2025
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