Effects of QCD-based equation of state on the structure and tidal deformability of compact stars in regularized 4D Einstein-Gauss-Bonnet gravity

We study quark star configurations in regularized four-dimensional Einstein-Gauss-Bonnet (4DEGB) gravity using a QCD-motivated equation of state with parameters $B_{\mathrm{eff}}$, $a_2$, and $a_4$. The modified Tolman-Oppenheimer-Volkoff equations, incorporating 4DEGB corrections, are solved to examine mass-radius relations, tidal deformability, and stability across a range of α, $a_2$, and $a_4$. Positive α or larger $a_2$ yields more massive, compact stars than in general relativity, with some configurations below the GR Buchdahl limit, potentially eliminating the mass gap with black holes. The dimensionless tidal deformability Λ decreases markedly with α and $a_2$, while $a_4$ has only a minor effect. Models consistent with NICER, GW170817, and HESS J1731−347 constraints remain dynamically stable and causal. Our results demonstrate that the interplay between higher-curvature gravity and QCD microphysics can produce observationally viable deviations from general relativity, offering promising targets for future multimessenger constraints on dense matter and alternative gravity theories.