Dark-energy-dark-matter admixed compact stars in 4D Einstein–Gauss–Bonnet gravity: constraints from recent observations

Abstract We investigate static equilibrium configurations of compact stars composed of an admixture of bosonic dark matter and dark energy within the framework of regularized four-dimensional Einstein–Gauss–Bonnet (4DEGB) gravity. The stellar interior is modeled as a two-fluid system in which self-interacting bosonic dark matter and Chaplygin-gas dark energy coexist and interact solely through gravity. Employing a scalar–tensor formulation of 4DEGB gravity, we derive the modified Tolman–Oppenheimer–Volkoff equations governing hydrostatic equilibrium and solve them numerically for a range of central densities. We systematically explore the impact of higher-curvature corrections by varying the Gauss–Bonnet coupling parameter, as well as the role of dark-matter microphysics by changing the bosonic particle mass. Our analysis shows that positive Gauss–Bonnet coupling significantly enhances the maximum supported mass and compactness of the configurations relative to the general relativistic limit, while remaining compatible with current observational constraints from GW170817, PSR J0740+6620, and HESS J1731–347. In contrast, variations in the bosonic dark-matter particle mass within the considered range induce only mild modifications to global stellar properties. The mass-central-density criterion, the relativistic adiabatic index, and the causality condition on the sound speed are all satisfied throughout the stellar interior, and stability is evaluated accordingly. These findings indicate that compact stars with dark-matter-dark-energy admixtures in regularized 4DEGB gravity are stable and feasible astrophysical configurations. They also emphasize the significant influence of higher-curvature effects on the macroscopic structure of these structures.