arXiv subjects

Surajit Chattopadhyay

Publications and source records attributed to Surajit Chattopadhyay.

At least 55 records · Page 3Linked to original sources

arXiv2016

Power-law and Logarithmic Entropy Corrected Holographic Dark Energy Models in Brans-Dicke Cosmology with Granda-Oliveros Cut-Off

In this paper, the cosmological implications of the Power Law Entropy Corrected Holographic Dark Energy (PLECHDE) and the Logarithmic Entropy Corrected Holographic Dark Energy (LECHDE) models in the context of Brans-Dicke (BD) cosmology for both non-interacting and interacting DE and Dark Matter (DM) are studied. As the system infrared cut-off, we choose the recently proposed Granda-Oliveros cut-off, which contains a term proportional to the first time derivative of the Hubble parameter and one term proportional to $H^2$, i.e. the Hubble parameter squared. We obtain the expressions of three quantities, i.e. the Equation of State (EoS) parameter $ω_D$, the deceleration parameter $q$ and the evolutionary form of the energy density parameter $Ω'_D$ of the PLECHDE and LECHDE models in a non-flat Universe for non-interacting and interacting DE and DM as well. Moreover, we investigate the limiting cases corresponding to: a) absence of entropy corrections; b) Einstein's gravity; and c) concomitantly absence of entropy corrections and Einstein's gravity. Furthermore, we consider the limiting case corresponding to the Ricci scale, which is recovered for some particular values of the parameters characterizing the Granda-Oliveros scale. We also study the statefinder diagnostic and the cosmographic parameters for both models considered in this work.

physics.gen-ph↗

arXiv2015

Consequences of three modified forms of holographic dark energy models in bulk-brane interaction

In this paper, we study the effects which are produced by the interaction between a brane Universe and the bulk in which the Universe is embedded. Taking into account the effects produced by the interaction between a brane Universe and the bulk, we derived the Equation of State (EoS) parameter $ω_D$ for three different models of Dark Energy (DE), \emph{i.e.} the Holographic DE (HDE) model with infrared (IR) cut-off given by the Granda-Oliveros cut-off, the Modified Holographic Ricci DE (MHRDE) model and a DE model which is function of the Hubble parameter $H$ squared and to higher derivatives of $H$. Moreover, we have considered two different cases of scale factor (namely, the power law and the emergent ones). A nontrivial contribution of the DE is observed to be different from the standard matter fields confined to the brane. Such contribution has a monotonically decreasing behavior upon the evolution of the Universe for the emergent scenario of the scale factor, while monotonically increasing for the power-law form of the scale factor $a(t)$.

gr-qc↗

arXiv2015

Holographic polytropic $f(T)$-gravity models

The present paper reports a study on the cosmological consequences arising from reconstructing $f(T)$ gravity through new holographic-polytropic dark energy. We assume two approaches, namely a particular form of Hubble parameter $H$ and a solution for $f(T)$. We obtain the deceleration parameter, effective equation of state as well as torsion equation of state parameters from total density and pressure in both cases. It is interesting to mention here that the deceleration and torsion equation of state represent transition from deceleration to acceleration phase. We study the statefinder parameters under both approaches which result that statefinder trajectories are found to attain $Λ$CDM point. The comparison with observational data represents consistent results. Also, we discuss the stability of reconstructed models through squared speed of sound which represents stability in late times.

gr-qc↗

arXiv2015

Reciprocal NUT spacetimes

In this paper, we study the \texttt{Ehlers' transformation} (sometimes called gravitational duality rotation) for \texttt{reciprocal} static metrics. First we introduce the concept of reciprocal metric. We prove a theorem which shows how we can construct a certain new static solution of Einstein field equations using a seed metric. Later we investigate the family of stationary spacetimes of such reciprocal metrics. The key here is a theorem from Ehlers', which relates any static vacuum solution to a unique stationary metric. The stationary metric has a magnetic charge. The spacetime represents Newman -Unti-Tamburino (NUT) solutions. Since any stationary spacetime can be decomposed into a $1+3$ time-space decomposition, Einstein field equations for any stationary spacetime can be written in the form of Maxwell's equations for gravitoelectromagnetic fields. Further we show that this set of equations is invariant under reciprocal transformations. An additional point is that the NUT charge changes the sign. As an instructive example, by starting from the reciprocal Schwarzschild as a spherically symmetric solution and reciprocal Morgan-Morgan disk model as seed metrics we find their corresponding stationary space-times. Starting from any static seed metric, performing the reciprocal transformation and by applying an additional Ehlers' transforation we obtain a family of NUT spaces with negative NUT factor (reciprocal NUT factors).

gr-qc↗

arXiv2015

Holographic dark energy reconstruction of $f(T,\mathcal{T})$ gravity

The present paper reports a holographic reconstruction scheme for $f(T,\mathcal T)$ gravity proposed in Harko et al. $\emph{JCAP}\; 12(2014)021$ where $T$ is the torsion scalar and $\mathcal{T}$ is the trace of the energy-momentum tensor considering future event horizon as the enveloping horizon of the universe. We have considered $f(T, \mathcal T)=T + γg(\mathcal T)$ and $f(T,\mathcal T) =β\mathcal T + g(T)$ for reconstruction. We observe that the derived $f(T,\mathcal T)$ models can represent phantom or quintessence regimes of the universe which are compatible with the current observational data.

gr-qc↗

arXiv2014

Holographic Dark Energy Models and Higher Order Generalizations in Dynamical Chern-Simons Modified Gravity

Dark Energy models are here investigated and studied in the framework of the Chern-Simons modified gravity model. We bring into focus the Holographic Dark Energy (HDE) model with Granda-Oliveros cut-off, the Modified Holographic Ricci Dark Energy (MHRDE) model and, moreover, a model with higher derivatives of the Hubble parameter as well. The relevant expressions of the scale factor a(t) for a Friedmann-Robertson-Walker Universe are derived and studied, and in this context, the evolution of the scale factor is shown to be similar to that one displayed by the modified Chaplygin gas in two of the above models.

gr-qc↗

arXiv2014

Can Holographic dark energy increase the mass of the wormhole?

In this work, we have studied accretion of dark energy (DE) onto Morris- Thorne wormhole with three different forms, namely, holographic dark energy, holographic Ricci dark energy and modified holographic Ricci dark energy . Considering the scale factor in power-law form we have observed that as the holographic dark energy accretes onto wormhole, the mass of the wormhole is decreasing. In the next phase we considered three parameterization schemes that are able to get hold of quintessence as well as phantom phases. Without any choice of scale factor we reconstructed Hubble parameter from conservation equation and dark energy densities and subsequently got the mass of the wormhole separately for accretion of the three dark energy candidates. It was observed that if these dark energies accrete onto the wormhole, then for quintessence stage, wormhole mass decreases up to a certain finite value and then again increases to aggressively during phantom phase of the universe.

gr-qc↗

arXiv2014

New holographic reconstruction of scalar field dark energy models in the framework of chameleon Brans-Dicke cosmology

Motivated by the work of Yang et al., \emph{Mod. Phys. Lett. A}, \textbf{26}, 191 (2011), we report a study on the New Holographic Dark Energy (NHDE) model with energy density given by $ρ_D=\frac{3ϕ^2}{4ω}(μH^2+ν\dot{H})$ in the framework of chameleon Brans-Dicke cosmology. We have studied a correspondence between the quintessence, the DBI-essence and the tachyon scalar field models with the NHDE model in the framework of chameleon Brans-Dicke cosmology. Deriving an expression of the Hubble parameter $H$ and, accordingly, $ρ_D$ in the context of chameleon Brans-Dicke chameleon cosmology, we have reconstructed the potentials and dynamics for these scalar field models. Furthermore, we have examined the stability for the obtained solutions of the crossing of the phantom divide under a quantum correction of massless conformally-invariant fields and we have seen that quantum correction could be small when the phantom crossing occurs and the obtained solutions of the phantom crossing could be stable under the quantum correction. It has also been noted that the potential increases as the matter-chameleon coupling gets stronger with the evolution of the universe.

gr-qc↗

arXiv2014

Pilgrim Dark Energy in $f(T, T_G)$ cosmology

We work on the reconstruction scenario of pilgrim dark energy" (PDE) in $f(T, T_G)$. In PDE model it is assumed that a repulsive force that is accelerating the Universe is phantom type with $(w_{DE}<-1)$ and it so strong that prevents formation of the black hole. We construct the $f(T, T_G)$ models and correspondingly evaluate equation of state parameter for various choices of scale factor. Also, we assume polynomial form of $f(T, T_G)$ in terms of cosmic time and reconstruct $H$ and $w_{DE}$ in this manner. Through discussion, it is concluded that PDE shows aggressive phantom-like behaviour for$s=-2$ in $f(T, T_G)$ gravity.

gr-qc↗

arXiv2014

Generalized second law of thermodynamics in QCD ghost f(G) gravity

Considering power-law for of scale factor in a flat FRW universe we reported a reconstruction scheme for $f(G)$ gravity based on QCD ghost dark energy. We reconstructed the effective equation of state parameter and observed "quintessence" behavior of the equation of state parameter. Furthermore, considering dynamical apparent horizon as the enveloping horizon of the universe we have observed that the generalized second law of thermodynamics is valid for this reconstructed $f(G)$ gravity.

gr-qc↗

arXiv2014

Holographic reconstruction of $f(G)$ Gravity for scale factors pertaining to Emergent, Logamediate and Intermediate scenarios

In this paper, we reconstruct the holographic dark energy in the framework of $f(G)$ modified theory of gravity, where $G$ is Gauss-Bonnet invariant. In this context, we choose the infrared cut-off as Granda-Oliveros cut-off which is proportional to the Hubble parameter $H$ and its first derivative with respect to the cosmic time $t$. We reconstruct $f(G)$ model with the inclusion of HDE and three well-known forms of the scale factor $a(t)$, i.e. the emergent, the logamediate and the intermediate scale factors. The reconstructed model as well as equation of state parameter are discussed numerically with the help of graphical representation to explore the accelerated expansion of the universe. Moreover, the stability of the models incorporating all the scale factors is checked through squared speed of sound $v_s^2$.

gr-qc↗

arXiv2014

Reconstruction of $f(G)$ Gravity with New Agegraphic Dark Energy Model

In this work, we consider the reconstruction scenario of new agegraphic dark energy (NADE) model and $f(G)$ theory of gravity with $G$ representing the Gauss-Bonnet invariant in the flat FRW spacetime. In this context, we assume a solution of the scale factor in power-law form and study the correspondence scenario. A new agegraphic $f(G)$ model is constructed and discussed graphically for the evolution of the universe. Using this model, we investigate the different eras of the expanding universe and stability with the help of the equation of state (EoS) parameter $ω_{eff}$ and squared speed of sound $v_s^2$, respectively. It is mentioned here that the reconstructed model represents the quintessence era of the accelerated expansion of the universe with instability. Moreover, the statefinder trajectories are studied and we find out that the model is not capable of reaching the $Λ$CDM phase of the universe.

gr-qc↗

arXiv2014

QCD ghost reconstruction of f(T) gravity in flat FRW universe

The present work reports a reconstruction scheme for f(T) gravity based on QCD ghost dark energy. Two models of f(T) have been generated and the pressure and density contributions due to torsion have been reconstructed. Two realistic models have been obtained and the effective equations of state have been studied. Also, the squared speed of sound has been studied to examine the stability of the models.

gr-qc↗

arXiv2014

Power Law and Logarithmic Ricci Dark Energy Models in Horava-Lifshitz Cosmology

In this work, we studied the Power Law and the Logarithmic Entropy Corrected versions of the Ricci Dark Energy (RDE) model in a spatially non-flat universe and in the framework of Hořava-Lifshitz cosmology. For the two cases containing non-interacting and interacting RDE and Dark Matter (DM), we obtained the exact differential equation that determines the evolutionary form of the RDE energy density parameter. Moreover, we obtained the expressions of the deceleration parameter $q$ and, using a parametrization of the equation of state (EoS) parameter $ω_D$ as $ω_D\left(z\right)=ω_0+ω_1 z$, we derived the expressions of both $ω_0$ and $ω_1$. We interestingly found that the expression of $ω_0$ is the same for both non-interacting and interacting case. The expression of $ω_1$ for the interacting case has strong dependence from the interacting parameter $b^2$. The parameters derived in this work are done in small redshift approximation and for low redshift expansion of the EoS parameter.

gr-qc↗

arXiv2013

A study on the dependence of the dimensionless Brans-Dicke parameter on the scalar field and their time dependence

The present paper reports a study on the dimensionless parameter $ω$ in Brans-Dicke theory. Based on a particular choice of scale factor $a$, we have investigated the signature flip of the deceleration parameter $q$ to see whether the transition from decelerated to accelerated expansion of the universe is achievable under this choice of scale factor. Restrictions on the parameters obtained for this choice of scale factor have been subsequently used for discussing the Brans-Dicke parameter for two choices of scalar fields $ϕ$. Moreover, analytical solutions for the Brans-Dicke parameter without any assumption about the scalar field have been obtained from the modified field equations through the choice of scale factor under consideration. Viable models have been obtained by comparing the results with observations.

gr-qc↗

arXiv2013

A Study on Ricci Dark Energy in Bulk-Brane Interaction

In this work we have investigated the effects of the interaction between a brane universe and the bulk in which it is embedded. Considering the effects of the interaction between a brane universe and the bulk we have obtained the equation of state for the interacting holographic Ricci dark energy density $ρ_Λ=3c^2 (\dot{H}+2 H^2)$ in the flat universe. We have investigated the impact of $c^2$ on the equation of state $ω_Λ$. Also, considering the power law for of the scale factor, we have observed that non-trivial contributions of dark energy which differ from the standard matter fields confined to the brane is increasing with the evolution of the universe.

gr-qc↗

arXiv2013

A dark energy with higher order derivatives of $H$ in the modified gravity $f(R,T)$

In this paper, we consider a recently proposed model of Dark Energy (DE) which contains three terms (one proportional to the squared Hubble parameter, one to the first derivative with respect to the cosmic time of the Hubble parameter and one proportional to the second derivative with respect to the cosmic time of the Hubble parameter) in the light of the $f\left(R,T \right)$ model of modified gravity, considering the particular model $f\left(R,T \right) = μR + νT$, with $μ$ and $ν$ two free positive constant parameters. Here $R$ and $T$ are the curvature and torsion scalars, respectively. In this work, we have found that the Hubble parameter $H$ exhibits a decaying behavior until redshifts of the order of $z\approx-0.5$ (when it starts to increase) and the time derivative of the Hubble parameter goes from negative to positive values for different redshifts. The equation of state (EoS) parameter of DE and the effective EoS parameter exhibit a transition from $ω<-1$ to $ω>-1$ (then the EoS parameters have a quintom-like behavior). We have also found that the said model can attain the late time accelerated phase of the universe. Using the statefinder parameters $r$ and $s$, we derived that the considered model can attaining the $Λ$CDM phase of the universe and can interpolate between dust and $Λ$CDM phase of the universe. Finally, studying the squared speed of sound $v_s^2$, we have seen that the model under consideration is classically stable in the earlier stage of the universe, but classically unstable in the current stage.

physics.gen-ph↗

arXiv2013

Extended holographic Ricci dark energy in chameleon Brans-Dicke cosmology

In the present work we have studied some features of the generalized Brans-Dicke (BD) model in which the scalar field is allowed to couple non-minimally with matter sector. Extended holographic Ricci dark energy (EHRDE) has been considered in the above framework of BD cosmology. Some restrictions have been derived for the BD parameter $ω$ and a stronger matter-chameleon coupling has been observed with expansion of the universe. In this framework, the equation of state parameter of EHRDE has behaved like quintom. Also, we have reconstructed the potential and coupling function for BD model for the EHRDE. It has been observed that potential function is increasing as the matter-chameleon coupling is getting stronger.

gr-qc↗