Abstract
In this work, we discuss the configuration of a gravastar (gravitational vacuum stars) in the context of f(R, ,T ) gravity by employing the Mazur–Mottola conjecture (Mazur and Mottola in Report No. LA-UR-01-5067, 2001; Mazur and Mottola, Proc Natl Acad Sci USA 101:9545, 2004). The gravastar is conceptually a substitute for a black hole theory as available in the literature and it has three regions with different equation of states. By assuming that the gravastar geometry admits a conformal Killing vector, the Einstein–Maxwell field equations have been solved in different regions of the gravastar by taking a specific equation of state as proposed by Mazur and Mottola. We match our interior spacetime to the exterior spherical region which is completely vacuum and described by the Reissner–Nordström geometry. For the particular choice of f(R,,T) of f(R, ,T )=R+2gamma T, here we analyze various physical properties of the thin shell and also present our results graphically for these properties. The stability analysis of our present model is also studied by introducing a new parameter eta and we explore the stability regions. Our proposed gravastar model in the presence of charge might be treated as a successful stable alternative of the charged black hole in the context of this version of gravity.
Highlights
The proposed model [10] is a static spherically symmetric perfect fluid model having three different regions designated by: (I) interior region (0 ≤ r1 < r ), (II) thin shell region (r1 < r < r2), (III) exterior region (r2 < r ) and it is separated by a thin shell of stiff matter
In the interior region of the gravastar the relation between pressure and density is given by p = −ρ, inside the thin shell it is described by p = ρ and in region III p = ρ = 0
For an uncharged model of the gravastar in (3 + 1)-D, the exterior spacetime is described by Schwarzschild geometry [12], whereas in the case of a charged gravastar model, the exterior spacetime is described by the Reissner–Nordström geometry [13,14]
Summary
The proposed model [10] is a static spherically symmetric perfect fluid model having three different regions designated by: (I) interior region (0 ≤ r1 < r ), (II) thin shell region (r1 < r < r2), (III) exterior region (r2 < r ) and it is separated by a thin shell of stiff matter. This particular choice of Lagrangian matter density is based upon the pioneering work of Harko et al [38] In their work, they presented the field equations of several particular models, corresponding to some explicit forms of the function f (R, T ). The non-conservation of the matter energy–momentum tensor is related to irreversible matter creation processes, in which there is an energy flow between the gravitational field and matter due to the geometry–matter coupling, with particles permanently added to the spacetime [93,94]. The term 2γ T induces a timedependent coupling between curvature and matter Substituting this particular form of the f (R, T ) function in Eq (3) the field equation for f (R, T ) gravity theory reads. We want to solve the field equations (29)–(31) in three different regions of the charged gravastar
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