Papers by Sagar Chandra Dey
We obtain a class of new anisotropic relativistic solution in Einstein Gauss-Bonnet (EGB) gravity... more We obtain a class of new anisotropic relativistic solution in Einstein Gauss-Bonnet (EGB) gravity with Finch-Skea metric in hydrostatic equilibrium. The relativistic solutions are employed to construct anisotropic stellar models for strange star with MIT Bag equation of state pr= ⅓ ( ρ - 4 Bg), where Bg is the Bag constants. Considering the mass and radius of a known star PSR J0348+0432 we construct stellar models in the framework of D- dimensions. We also predict the mass and radius of stars for different model parameters. The Gauss-Bonnet coupling term (α) plays an important role in determining the density, pressure, anisotropy profiles and other features. The stability of the stellar models are probed analyzing the different energy conditions, variation of sound speed and adiabatic stability conditions inside the star. The central density and pressure of a star in EGB gravity are found to have higher values compared to that one obtains in Einstein gravity (α =0). We also explore ...
The European Physical Journal C
We present a new class of relativistic anisotropic stellar models with spherically symmetric matt... more We present a new class of relativistic anisotropic stellar models with spherically symmetric matter distribution in Einstein Gauss–Bonnet (EGB) gravity. A higher dimensional Finch–Skea geometry in the theory is taken up here to construct stellar models in hydrostatic equilibrium. The Gauss–Bonnet term is playing an important role in accommodating neutron stars. We study the physical features namely, the energy density, the radial and tangential pressures and the suitability of the models. It is found that the equation of state of such stars are non-linear which is determined for a given mass and radius of known stars. The stability of the stellar models are also explored for a wide range of values of the model parameters.
International Journal of Geometric Methods in Modern Physics, 2022
Rényi Holographic Dark Energy (RHDE) Models have been studied in different dimensions considering... more Rényi Holographic Dark Energy (RHDE) Models have been studied in different dimensions considering a flat FRW metric and subsequently exploring the nature of evolution of different cosmological parameters. It is seen that the number of dimensions affect the evolution of the cosmological parameters and the transition of the universe from decelerating to accelerating phase. The statefinder diagnostics have been performed and it is seen that the model corresponds to the [Formula: see text] model for the present and future universe.
Journal of Cosmology and Astroparticle Physics, 2021
Gravastars have been considered as a feasible alternative to black holes in the past couple of de... more Gravastars have been considered as a feasible alternative to black holes in the past couple of decades. Stable models of gravastar have been studied in many of the alternative gravity theories besides standard General Relativity (GR). The Rastall theory of gravity is a popular alternative to GR, specially in the cosmological and astrophysical context. Here, we propose a stellar model under the Rastall gravity following Mazur-Mottola's [1, 2] conjecture. The gravastar consists of three regions, viz., (I) Interior region, (II) Intermediate shell region, and (III) Exterior region. The pressure within the interior core region is assumed with a constant negative matter-energy density which provides a repulsive force over the entire thin shell region. The shell is assumed to be made up of fluid of ultrarelativistic plasma which follows the Zel'dovich's conjecture of stiff fluid [3, 4]. It is also assumed that the pressure is proportional to the matter-energy density according to Zel'dovich's conjecture, which cancel the repulsive force exerted by the interior region. The exterior region is completely vacuum which is described by the Schwarzschild-de Sitter solution. Under all these specifications we obtain a set of exact and singularity-free solutions of the gravastar model presenting several physically valid features within the framework of Rastall gravity. The physical properties of the shell region namely, the energy density, proper length, total energy and entropy are explored. The stability of the gravastar model is investigated using the surface redshift against the shell thickness and maximizing the entropy of the shell within the framework of Rastall gravity.
General Relativity and Gravitation, 2021
Wormhole solutions obtained by Morris and Thorne (MT) in general relativity (GR) is investigated ... more Wormhole solutions obtained by Morris and Thorne (MT) in general relativity (GR) is investigated in a modified theory of gravity. In the gravitational action, we consider f (R, T) which is a function of the Ricci scalar (R) and the trace of the energy momentum tensor (T). In the framework of a modified gravity described by f (R, T) = R + αR 2 + λT , where α and λ are constants, MT wormhole solutions (WH) with normal matter are obtained for a relevant shape function. The energy conditions are probed at the throat and away from the throat of the WH. It is found that the coupling parameters, α and λ in the gravitational action play an important role to decide the matter composition needed. It is found that for a given λ, WH exists in the presence of exotic matter at the throat when α < 0. However, it is demonstrated that the WH exists without exotic matter when α > 0 in the modified gravity. Two different shape functions are analyzed for the WH solutions that admits with or without exotic matter. It is noted that in a modified gravity MT WH permits even with normal matter which is not possible in GR. It is shown that a class of WH solutions exist with anisotropic fluid for λ = −8π. However, for flat asymptotic regions with anisotropic fluids WH solutions cannot be realized for λ = −8π. All the energy conditions are found consistent with the hybrid shape function indicating existence of WH even with normal matter for λ → 0.
Classical and Quantum Gravity, 2020
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Papers by Sagar Chandra Dey