Anisotropic cosmologies with ghost dark energy models in f (R, T) gravity

Fayaz, V.; Hossienkhani, H.; Zarei, Zahra; Azimi, N.

doi:10.1140/epjp/i2016-16022-x

Cited by 33 publications

(21 citation statements)

References 59 publications

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“…One can note that such a dependence on T may come from the presence of an imperfect fluid or from the consideration of quantum effects. The application of f (R, T ) gravity theory to different cosmological [30][31][32][33][34][35][36][37][38][39][40][41][42] realm can be noted in the literature. Among several astrophysical applications it is worthy of mentioning the Refs.…”

Section: Introductionmentioning

confidence: 99%

Gravastars in f(R,T) gravity

Das¹,

Ghosh²,

Guha³

et al. 2017

Phys. Rev. D

190

118

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We propose a unique stellar model under the f (R, T ) gravity by using the conjecture of MazurMottola [P. Mazur and E. Mottola, Report number: LA-UR-01-5067., P. Mazur and E. Mottola, Proc. Natl. Acad. Sci. USA 101, 9545 (2004).] which is known as gravastar and a viable alternative to the black hole as available in literature. This gravastar is described by the three different regions, viz., (I) Interior core region, (II) Intermediate thin shell, and (III) Exterior spherical region. The pressure within the interior region is equal to the constant negative matter density which provides a repulsive force over the thin spherical shell. This thin shell is assumed to be formed by a fluid of ultrarelativistic plasma and the pressure, which is directly proportional to the matter-energy density according to Zel'dovich's conjecture of stiff fluid [Y.B. Zel'dovich, Mon. Not. R. Astron. Soc. 160, 1 (1972).], does counterbalance the repulsive force exerted by the interior core region. The exterior spherical region is completely vacuum and assumed to be de Sitter spacetime which can be described by the Schwarzschild solution. Under this specification we find out a set of exact and singularity-free solution of the gravastar which presents several other physically valid features within the framework of alternative gravity.

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Section: Introductionmentioning

confidence: 99%

Gravastars in f(R,T) gravity

Das¹,

Ghosh²,

Guha³

et al. 2017

Phys. Rev. D

190

118

View full text Add to dashboard Cite

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“…Following Harko et al [27], in the present article we consider simple linear form of the function f (R, T ) as f (R, T ) = f (R) + 2f (T ), where f (R) = R and f (T ) = 2χT . This form of the function f (R, T ) has been broadly used by several authors [75][76][77][78][79][80][81][82][83][84][85][86][87][88]. Now substituting the assumed form of the function f (R, T ) into Eq.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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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.

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“…Chattopadhyay [19] explored stability of cosmic evolution using cosmological parameters. Fayaz et al [20] investigated this model in f (R, T ) gravity for Bianchi-I universe and concluded that their results favor the current behavior of the universe.…”

Section: Introductionmentioning

confidence: 99%

Ghost dark energy model in f(G) gravity

Sharif

Saba

2019

Chinese Journal of Physics

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In this paper, we investigate cosmological consequences of ghost dark energy model in modified Gauss-Bonnet gravity. We construct ghost dark energy f (G) model by using correspondence scenario for both interacting and non-interacting schemes. For this purpose, we consider FRW universe with pressureless matter and power-law scale factor. We examine the behavior of equation of state parameter and check the stability of ghost dark energy model through squared speed of sound parameter. We also analyze the behavior of phase planes like ω ef f − ω ′ ef f and r − s graphically. It is found that the equation of state parameter represents quintessence era for non-interacting while phantom phase of the universe for interacting case. The squared speed of sound indicates stable ghost dark energy model for both cases.The ω ef f − ω ′ ef f plane shows thawing region for non-interacting while freezing region for interacting case. The r − s plane corresponds to Chaplygin gas model in both scenarios. We conclude that ghost dark energy model describes evolution of the universe for appropriate choice of parameters.The well-known phenomenon of accelerated expansion of the universe is usually explained by the exotic type force known as dark energy (DE). The cosmological constant is the simplest DE model and is the base of ΛCDM model. Despite showing the consistent behavior with all observational data, ΛCDM model undergoes several difficulties like fine tuning and cosmic coincidence problem [1]. In order to substantiate the behavior of DE, researchers used two different approaches, firstly the dynamical DE models [2] and secondly the modified gravity theories [3].A dynamical DE model, known as Veneziano ghost DE (GDE) has been introduced in late 70's by Veneziano [4]. This has significant non-trivial physical properties for the expanding universe or in spacetime having nontrivial topological formation. The existence of Veneziano GDE is supposed to resolve U(1) problem [5]. The GDE has little contribution to the vacuum energy density in a curved spacetime. It is proportional to Λ 3 QCD H, where Λ QCD and H are the quantum chromodynamics (QCD) mass scale and Hubble parameter, respectively [6]. For measures Λ QCD ∼ 100MeV and H ∼ 10 −33 MeV , Λ 3 QCD H gives approximately (10 −3 eV ) 4 to the observed DE density. This numeric value is incredible to offer the necessary exotic force for accelerating universe and also alleviates the fine tuning problem.The Gauss-Bonnet (GB) theory is incredibly motivating theory as it shows consistent behavior with solar system constraints. The GB invariant has the expression as G = R αρδσ R αρδσ − 4R αρ R αρ + R 2 , where R, R αρ and R αρδσ stand for the Ricci scalar, Ricci tensor and Riemann curvature tensor, respectively. This invariant is a four-dimensional topological expression with restriction for spin-2 ghost instability. Nojiri and Odintsov [7] proposed f (G) gravity by adding a generic function in the Einstein-Hilbert action. This amazing theory effectively describes the early and late-time cosmic...

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Anisotropic cosmologies with ghost dark energy models in f (R, T) gravity

Cited by 33 publications

References 59 publications

Gravastars in f(R,T) gravity

Gravastars in f(R,T) gravity

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

Ghost dark energy model in f(G) gravity

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