Anisotropic strange stars under simplest minimal matter-geometry coupling in the f ( R,T ) gravity

Abstract

We study strange stars in the framework of f (R, T ) theory of gravity. To provide exact solutions of the field equations it is considered that the gravitational Lagrangian can be expressed as the linear function of the Ricci scalar R and the trace of the stress-energy tensor T , i.e. f (R, T ) = R + 2χT , where χ is a constant. We also consider that the strange quark matter (SQM) distribution inside the stellar system is governed by the phenomenological MIT Bag model equation of state (EOS), given as pr = 1 3 (ρ − 4 B), where B is the Bag constant. Further, for a specific value of B and observed values of mass of the strange star candidates we obtain the exact solution of the modified Tolman-Oppenheimer-Volkoff (TOV) equation in the framework of f (R, T ) gravity and have studied in detail the dependence of the different physical parameters, like the metric potentials, energy density, radial and tangential pressures and anisotropy etc., due to the chosen different values of χ. Likewise in GR, as have been shown in our previous work [Deb et al., Ann. Phys. (Amsterdam) 387, 239 (2017)] in the present work also we find maximum anisotropy at the surface which seems an inherent property of the strange stars in modified f (R, T ) theory of gravity. To check the physical acceptability and stability of the stellar system based on the obtained solutions we have performed different physical tests, viz., the energy conditions, Herrera cracking concept, adiabatic index etc. In this work, we also have explained the effects, those are arising due to the interaction between the matter and the curvature terms in f (R, T ) gravity, on the anisotropic compact stellar system. It is interesting to note that as the values of χ increase the strange stars become more massive and their radius increase gradually so that eventually they gradually turn into less dense compact objects. The present study reveals that the modified f (R, T ) gravity is a suitable theory to explain massive stellar systems like recent magnetars, massive pulsars and super-Chandrasekhar stars, which can not be explained in the framework of GR. However, for χ = 0 the standard results of Einsteinian gravity are retrieved.

Modified Einstein's gravity to probe the sub- and super-Chandrasekhar limiting mass white dwarfs: a new perspective to unify under- and over-luminous type Ia supernovae

“…Starobinsky first used modified theory of Einstein's gravity to explain some of these problems in cosmology [5]. Eventually many theories and models have been proposed to explain various epochs of the universe [6][7][8] and physical properties of various astrophysical objects [9][10][11]. One of the theories which is commonly used is the f (R) gravity, first proposed by Buchdahl [12].…”

Anisotropic quark stars in f(R, T) gravity

“…Sharif and Siddiqa [38] investigated the effect of higher curvature terms present in f (R, T ) model on the evolution of compact stars using polytropic as well as MIT bag model EoS and obtained stable structures for particular values of the model parameters. Deb et al [39] evaluated the solutions of f (R, T ) field equations with anisotropic matter distribution for strange quark stars using MIT bag model EoS and studied the physical features of LMC X-4 as the representative of strange stars.…”

Relativistic compact stars with dark matter density profile

“…The MIT Bag Model commands a simple linear equation of state p r (r ) = 1 3 {ρ(r ) − 4B g }, where B g is known as the bag constant. The physical properties of compact stars have been studied by using the MIT Bag model equation of state in [35][36][37][38].…”