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Subenoy Chakraborty

Publications and source records attributed to Subenoy Chakraborty.

At least 145 records · Page 8Linked to original sources
arXiv2013

Will there be again a transition from acceleration to deceleration in course of the dark energy evolution of the universe?

In this work we consider the evolution of the interactive dark fluids in the background of homogeneous and isotropic FRW model of the universe. The dark fluids consist of a warm dark matter and a dark energy and both are described as perfect fluid with barotropic equation of state. The dark species interact non-gravitationally through an additional term in the energy conservation equations. An autonomous system is formed in the energy density spaces and fixed points are analyzed. A general expression for the deceleration parameter has been obtained and it is possible to have more than one zero of the deceleration parameter. Finally, vanishing of the deceleration parameter has been examined with some examples.

gr-qc↗
arXiv2013

An Alternative f (R, T) Gravity Theory and the Dark Energy Problem

Recently, a generalized gravity theory was proposed by Harko etal where the Lagrangian density is an arbitrary function of the Ricci scalar R and the trace of the stress-energy tensor T, known as F(R,T) gravity. In their derivation of the field equations, they have not considered conservation of the stress-energy tensor. In the present work, we have shown that a part of the arbitrary function f(R,T) can be determined if we take into account of the conservation of stress-energy tensor, although the form of the field equations remain similar. For homogeneous and isotropic model of the universe the field equations are solved and corresponding cosmological aspects has been discussed. Finally, we have studied the energy conditions in this modified gravity theory both generally and a particular case of perfect fluid with constant equation of state.

physics.gen-ph↗
arXiv2013

Dilatonic Scalar Field: A Dynamical System Analysis

The work deals with homogeneous and isotropic, flat FRW model of the universe which is filled up with non-interacting dark matter and dark energy to compatible with recent observational evidences. By choosing the dark energy in the form of a dilatonic scalar field, the evolution equations are reduced to an autonomous system. A phase space analysis is done around the critical points and stability criteria is examined. Finally, cosmological implications of the nature of the critical points are discussed.

gr-qc↗
arXiv2012

Is thermodynamics of the universe bounded by the event horizon a Bekenstein system?

In this brief communication, we have studied the validity of the first law of thermodynamics for the universe bounded by event horizon with two examples. The key point is the appropriate choice of the temperature on the event horizon. Finally, we have concluded that universe bounded by the event horizon may be a Bekenstein system and the Einstein's equations and the first law of thermodynamics on the event horizons are equivalent.

gr-qc↗
arXiv2012

Universe Bounded By Event Horizon: A Non equilibrium Thermodynamic Prescription

The present work deals with universe bounded by the cosmological event horizon as a thermodynamical system which is irreversible in nature.Using non-equilibrium thermodynamical approach the entropy variation on the event horizon has been evaluated.The additional term in the entropy variation depends on the irreversible process parameter.Finally,two dark energy models are presented and results are analyzed.

physics.gen-ph↗
arXiv2012

Hawking-like radiation from the apparent horizon in an FRW Universe : Quantum Corrections

In this paper we study Hawking-like radiation in a FRW-Universe using semi-classical tunnelling approach and the Hamilton-Jacobi method. Radial null geodesics are used to picture the process as a "tunnelling" of particles from behind the apparent horizon and Hawking -like temperature has been calculated. Quantum corrections have been evaluated in the Hamilton-Jacobi Method by solving Klein-Gordan wave equation and the temperature agrees at the semiclassical level. Also it is found that Hamilton-Jacobi formalism does not depend on the choice of the coordinate system. Finally, leading order corrections to entropy has been calculated.

gr-qc↗
arXiv2012

Quantum tunnelling for Hawking radiation from a dynamical Black Hole

The paper deals with Hawking radiation related to non-static spherically symmetric black hole. Quantum corrections are incorporated using Hamilton-Jacobi method beyond semi-classical approximation. It is found that different order correction terms satisfy identical differential equation as the semiclassical action and are solved by a typical technique. It has been shown that with proper choice of the proportionality factors, one loop back reaction effect in the space time can be obtained. Finally, using the law of black hole mechanics, a general modified form of the black hole entropy is obtained considering modified Hawking temperature.

gr-qc↗
arXiv2012

Quantum Tunnelling of non-zero mass particle and evolution of the horizon for a static black hole

In this work, we study Hawking radiation from a general static black hole due to tunnelling of particle having nonzero mass. Hawking temperature has been calculated using both the tunnelling method and the Hamilton-Jacobi method and the results do no depend on the mass of the particle. Due to complicated form of the equations involved quantum corrections are evaluated only upto first order and it is possible to interprete the correction term as loop corrections of the back reaction effects in the space time. Finally, modified expressions for entropy and surface gravity has been evaluated and it is found that the leading order correction term to the entropy is not necessarily logarithmic in nature.

gr-qc↗
arXiv2012

Lemaitre-Tolman-Bondi model of the universe and Hawking radiation of a dynamical horizon

The paper deals with anisotropic spherically symmetric Lemaitre-Tolman-Bondi model of the universe bounded by the apparent horizon. Using Hamilton-Jacobi method for both massive and massless test particles, we are able to show that the temperature associated with the apparent horizon due to Hawking radiation is the usual Hawking Temperature. Also the usual Lemaitre-Tolman-Bondi model and the transformed r-gauge Lemaitre-Tolman-Bondi model are shown to be equivalent. Finally, the results of Tunneling approach agree with the Hamiltonian-Jacobi method.

gr-qc↗
arXiv2012

Particle motion in the field of a five-dimensional charged black hole

In this paper, we have investigated the geodesics of neutral particles near a five-dimensional charged black hole using a comparative approach. The effective potential method is used to determine the location of the horizons and to study radial and circular trajectories. This also helps us to analyze the stability of radial and circular orbits. The radius of the innermost stable circular orbits have also been determined. Contrary to the case of massive particles for which, the circular orbits may have up to eight possible values of specific radius, we find that the photons will only have two distinct values for the specific radii of circular trajectories. Finally we have used the dynamical systems analysis to determine the critical points and the nature of the trajectories for the timelike and null geodesics.

gr-qc↗
arXiv2011

Holographic Dark Energy Model: State Finder Parameters

In this work, we have studied interacting holographic dark energy model in the background of FRW model of the universe. The interaction is chosen either in linear combination or in product form of the matter densities for dark matter and dark energy. The IR cut off for holographic dark energy is chosen as Ricci's length scale or radius of the future event horizon. The analysis is done using the state finder parameter and coincidence problem has been graphically presented. Finally, universal thermodynamics has been studied using state finder parameters.

physics.gen-ph↗
arXiv2011

Interacting Holographic Dark Energy at the Ricci scale and Dynamical system

In this work, we consider homogeneous and isotropic FRW model of the universe, filled with interacting dark matter and dark energy. The dark matter is chosen as usual in the form of dust while dark energy is holographic in nature with IR cut off at the Ricci's length and it is in the form of a perfect fluid with variable equation of state. We have chosen the interaction term of the following two types: (i) a linear combination of the matter density of the two fluids, (ii) a product of the two matter densities. For both the choices the evolution equations are transformed to an autonomous system and the corresponding critical points are analyzed. Finally, for the first choice of the interaction term the evolution of the ratio of the energy densities has been studied from the point of view of the present coincidence problem.

gr-qc↗
arXiv2011

Universal Thermodynamics with state finder parameters: A general prescription

The work deals with universal thermodynamics for flat FRW model, considering interacting $n-$fluid system. By introducing the state finder parameters, the feasible regions in the $\{r,s\}-$plane has been examined for the validity of the Generalized Second Law of Thermodynamics. A general prescription for the evolution of the horizon has been derived for general non-static spherically symmetric space time and then it is applied to FRW universe. A general restriction on the matter has been found for the validity of GSLT.

physics.gen-ph↗
arXiv2011

Trajectory around a spherically symmetric non-rotating black hole

Trajectory of a test particle or a photon around a general spherical black hole is studied and bending of light trajectory is investigated. Pseudo-Newtonian gravitational potential describing the gravitational field of the black hole is determined and is compared with the related effective potential for test particle motion. As an example, results are presented for Reissner-Nordström black hole.

gr-qc↗
arXiv2011

Five-dimensional warped product space-time with time-dependent warp factor and cosmology of the four-dimensional universe

In this paper, we have studied a 5-dimensional warped product space-time with a time-dependent warp factor. This warp factor plays an important role in localizing matter to the 4-dimensional hypersurface constituting the observed universe and leads to a geometric interpretation of dynamical dark energy. The five-dimensional field equations are constructed and its solutions are obtained. The nature of modifications produced by this warp factor in the bulk geometry is discussed. The hypersurface is described by a flat FRW-type metric in the ordinary spatial dimension. It is found that the effective cosmological constant of the four-dimensional universe is a variable quantity monitored by the time-dependent warp factor. The universe is initially decelerated, but subsequently makes a transition to an accelerated phase at later times.

gr-qc↗