Color–flavor locked strange stars in 4D Einstein–Gauss–Bonnet gravity

Abstract

This work is devoted to the recently introduced Einstein–Gauss–Bonnet gravity in four dimensions. This theory can bypass Lovelock’s theorem and avoids Ostrogradsky instability. The integrated part of this theory is the GB term which gives rise to a non-trivial contribution to the gravitational dynamics in the limit D→4. Our main interest is to explore a class of static, spherically symmetric compact objects made of strange matter. It is believed that at ultra-high densities, quark matter may exist in a variety of superconducting states, namely, the Color–Flavor-Locked (CFL) phase. With these equations of state (EoS) we explore the conditions under which compact stars are stable under extreme conditions in the context of 4D EGB gravity. In addition, the mass–radius relation is examined and the effects of the coupling constant ‘α’ on the stellar model, energy conditions, speed of sound and adiabatic stability are studied. With the aim to find observational constraints on the GB constant of 4D EGB gravity, the mass–radius curve is determined satisfying the maximum mass constraint of M∼2M⊙ for neutron stars. This feature may be relevant in view of recent observations claiming the existence of stable compact quark stars (hybrid neutron stars or strange stars).