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PreprintarXiv licencearXiv

Quark stars in regularized 4D Einstein-Gauss-Bonnet gravity: A perturbative QCD equation of state

  • Anirudh Pradhan
  • Safiqul Islam
  • Safyan Mukhtar
  • Santosh Kumar Dixit
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Abstract

We investigate the equilibrium structure and stability of selfbound quark stars in the framework of regularized four-dimensional Einstein--Gauss--Bonnet (4DEGB) gravity, employing the perturbative QCD equation of state of Fraga, Kurkela and Vuorinen [1]. The equation of state, parameterised by a single renormalization-scale parameter X, contains no effective bag constant and defines the stellar surface entirely through the vanishing of the quark-matter pressure. We solve the modified Tolman-Oppenheimer--Volkoff equations derived from the scalar--tensor formulation of 4DEGB gravity for X ∈ {3, 4} and Gauss--Bonnet coupling α∈ {0, 1, 10} km2. For the soft EOS (X = 3), the maximum mass increases from 2.0431 M⊙ (GR) to 2.5013 M⊙ at α= 10 km2, with only the latter entering the PSR~J0952−0607 mass band. For the stiff EOS(X = 4), the GR baseline already yields 3.0415 M⊙, and all configurations exceed both the GW190814 secondary mass and the PSR~J0952−0607 constraint. The compactness C = M/R at maximum mass ranges from $0.2531$ to $0.3123$ across all configurations, remaining well below the Buchdahl bound throughout. Radial profiles of the squared speed of sound confirm that cs2 < 1/3 holds pointwise throughout the stellar interior for all parameter choices, establishing that the quark matter remains sub-conformal and causal inside the maximum-mass star. These results demonstrate that higher-curvature corrections in 4DEGB gravity systematically enhance the maximum supported mass of perturbative QCD quark stars, with the stiff (X = 4) branch already exceeding the most massive compact objects currently observed even at the GR level, while the soft (X = 3) branch requires alphaGB ∼ 10 km2 to approach those thresholds.

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Cite

BibTeXRIS
BibTeX
@misc{pradhan2026quark,
  title = {{Quark stars in regularized 4D Einstein-Gauss-Bonnet gravity: A perturbative QCD equation of state}},
  author = {Anirudh Pradhan and Safiqul Islam and Safyan Mukhtar and Santosh Kumar Dixit},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.13227},
  eprint = {2609.13227},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.13227},
}
RIS
TY  - UNPB
TI  - Quark stars in regularized 4D Einstein-Gauss-Bonnet gravity: A perturbative QCD equation of state
AU  - Anirudh Pradhan
AU  - Safiqul Islam
AU  - Safyan Mukhtar
AU  - Santosh Kumar Dixit
PY  - 2026
DA  - 2026/09/01
PB  - arXiv
DO  - 10.48550/arxiv.2609.13227
UR  - https://arxiv.org/abs/2609.13227
AB  - We investigate the equilibrium structure and stability of selfbound quark stars in the framework of regularized four-dimensional Einstein--Gauss--Bonnet (4DEGB) gravity, employing the perturbative QCD equation of state of Fraga, Kurkela and Vuorinen [1]. The equation of state, parameterised by a single renormalization-scale parameter X, contains no effective bag constant and defines the stellar surface entirely through the vanishing of the quark-matter pressure. We solve the modified Tolman-Oppenheimer--Volkoff equations derived from the scalar--tensor formulation of 4DEGB gravity for X ∈ {3, 4} and Gauss--Bonnet coupling α∈ {0, 1, 10} km^2. For the soft EOS (X = 3), the maximum mass increases from 2.0431 M_⊙ (GR) to 2.5013 M_⊙ at α= 10 km^2, with only the latter entering the PSR~J0952−0607 mass band. For the stiff EOS(X = 4), the GR baseline already yields 3.0415 M_⊙, and all configurations exceed both the GW190814 secondary mass and the PSR~J0952−0607 constraint. The compactness C = M/R at maximum mass ranges from $0.2531$ to $0.3123$ across all configurations, remaining well below the Buchdahl bound throughout. Radial profiles of the squared speed of sound confirm that c_s^2 < 1/3 holds pointwise throughout the stellar interior for all parameter choices, establishing that the quark matter remains sub-conformal and causal inside the maximum-mass star. These results demonstrate that higher-curvature corrections in 4DEGB gravity systematically enhance the maximum supported mass of perturbative QCD quark stars, with the stiff (X = 4) branch already exceeding the most massive compact objects currently observed even at the GR level, while the soft (X = 3) branch requires alphaGB ∼ 10 km^2 to approach those thresholds.
ER  -