Massive compact stars beyond two solar masses: quark stars admixed with dark matter in regularized 4D Einstein–Gauss–Bonnet gravity

Abstract We investigate massive compact stars composed of quark matter admixed with bosonic dark matter in regularized four-dimensional Einstein–Gauss–Bonnet gravity. The stellar interior is modeled as a two-fluid system, in which quark matter follows the MIT bag model and dark matter is described by self-interacting bosonic particles in the Thomas–Fermi regime. Numerical integration of the modified Tolman–Oppenheimer–Volkoff equations reveals that positive Gauss–Bonnet coupling significantly enhances the maximum gravitational mass, with configurations reaching up to 2. 5~M 2. 5 M ⊙, thereby enabling compact stars to exceed two solar masses. The resulting mass–radius relations are consistent with observational constraints from GW170817, PSR J0348+0432, PSR J0952-0607, and HESS J1731-347. Comprehensive stability analysis shows that the equilibrium sequences satisfy the Harrison–Zeldovich–Novikov static stability criterion up to the maximum-mass turning point, while representative stable-branch configurations exhibit adiabatic indices exceeding =4/3 γ = 4 / 3 and maintain subluminal sound speeds throughout the stellar interior. Our results demonstrate that the combined effects of quark matter, dark matter, and higher-curvature corrections provide a robust framework for describing ultra-massive compact stars in the multi-messenger era.