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Probing the nonstrange quark star equation of state with compact stars and gravitational waves

Shu-Peng Wang1, Zhen-Yan Lu1,*, Zhi-Jun Ma1,2,†, Rong-Yao Yang1,‡, Jian-Feng Xu3,§, and Xiangyun Fu1

  • *Contact author: luzhenyan@hnust.edu.cn
  • †Contact author: mazhijun@hnust.edu.cn
  • ‡Contact author: ryyang@seu.edu.cn
  • §Contact author: xujf@squ.edu.cn
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Phys. Rev. D 112, 094036 – Published 19 November, 2025

DOI: https://doi.org/10.1103/d7pv-1dqt

Abstract

A recent study shows that incorporating a new term into the thermodynamic potential density, as required by the thermodynamic consistency criterion, can effectively resolve the thermodynamic inconsistency problems of the conventional perturbative QCD model. This additional term plays a crucial role in resolving inconsistencies at relatively low densities and becomes negligible at extremely high densities. Within this revised perturbative QCD model, we find that if we require only that the energy per baryon of up-down (ud) quark matter exceeds 930 MeV so as not to contradict the standard nuclear physics, the maximum mass of an ud quark star allowed by the revised perturbative QCD model can reach up to 2.17M⊙. From this perspective, the observed 2.14M⊙ pulsar PSR J0740+6620 may be an ud quark star. However, if we further impose the constraint that the tidal deformability of a 1.4M⊙ ud quark star must be consistent with the GW170817 event, the maximum mass allowed by the revised perturbative QCD model would decrease to no more than 2.08M⊙. Consequently, our results suggest that the compact object with a mass of 2.50−2.67M⊙, as observed in the GW190814 event, cannot be an ud quark star, according to the revised perturbative QCD model.

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Phys. Rev. D 112, 094036– Published 19 November, 2025
  • Received 4 August 2025
  • Accepted 28 October 2025
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