arXiv subjects

Surajit Chattopadhyay

Publications and source records attributed to Surajit Chattopadhyay.

At least 37 records · Page 2Linked to original sources

arXiv2024

Implementation of cosmological bounce inflation with Nojiri-Odintsov generalized holographic dark fluid

The current work reports a study on bounce cosmology with a highly generalized holographic dark fluid inspired by S. Nojiri and S. D. Odintsov, 2017, European Physical Journal C, 77, pp.1-8. The holographic dark fluid that is mostly used for late-time acceleration has been implemented to reconstruct towards realisation of cosmological bounce. We first used the most generalized Nojiri-Odintsov(NO) cutoff to implement the holographic dark fluid. Accordingly, we have reconstructed this dark fluid via some solutions of scale factors. With those solutions, we have explored the evolution of different cosmological parameters. We have examined the effects of each reconstructed parameter in the context of the realization of the cosmic bounce. Next, we use the analytical inferences of the scalar spectral index, tensor-to-scalar ratio, and slow-roll characteristics of the model to study a bounce inflationary scenario. Since inflation is usually associated with the existence of scalar fields, we looked at a possible relationship between NO generalized holographic dark energy and scalar field models. Plotting the evolution of the potential that results from the scalar fields against time. Finally, we investigated the GSL of thermodynamics in the pre-and post-bounce scenarios.

physics.gen-ph↗

arXiv2024

Relativistic model of anisotropic star with Bose-Einstein density depiction in $f(T)$ gravity

This article presents a new model for anisotropic compact stars that are confined to physical dark matter in the background of $f(T)$ teleparallel gravity. The model is based on the equation of state (EoS) of the bag model type and the Bose-Einstein dark matter density profile. The derived solutions meet the energy conditions, the causality conditions, and the required conditions on the stability factor and adiabatic index, indicating that they are physically well-behaved and represent the physical and stable matter configuration. We also determine the maximum mass, surface redshift, and compactness parameter at the surface. Interestingly, all of these numbers fall within the specified range, supporting the physical viability of our proposal. Additionally, the various masses that are derived for varying the model parameter $k$ correspond to five compact, realistic compact objects, including LMC X-4, Her X-1, 4U 1538-52, SAX J1808.4-3658, and Cen X-3. We have also illustrated the radially symmetric profiles of energy density and the moment of inertia for non-rotating stars.

gr-qc↗

arXiv2024

Thermodynamics of the most generalized form of Holographic Dark Energy and some particular cases with Corrected Entropies

The holographic cut-off in generalized dark energy (HDE) formalism depends on its cut-off. Following this, a four-parameter generalized entropy has recently been developed. It reduces to various known entropies for appropriate parameter limits in the study of Odintsov, S. D., S. DOnofrio, and T. Paul. (2023) Physics of the Dark Universe, 42 pp: 101277. In the current work, we investigate the evolution of the universe in its early phase and late phase within the framework of entropic cosmology, where the entropic energy density functions are reconstructed within the framework of the equivalence of holographic dark energy and four-parameter generalized entropy (Sg). Along with the reconstruction as mentioned earlier scheme, in this study, we demonstrate that an extensive variety of dark energy (DE) models can be considered distinct and particular candidates for the most generalized four-parameter entropic HDE family, each having their cut-off. We examined several entropic dark energy models in this regard, including the generalized holographic dark energy with Nojiri-Odintsov(NO) cut-off, the Barrow entropic HDE (BHDE) with particle horizon as IR cut-off, the Tsallis entropic HDE (THDE) with future event horizon as IR cut-off, all of three cases are particular cases of the most generalized four parameter entropic holographic dark energy. Inspired by S. Nojiri, and S. D. Odintsov (2006) (General Relativity and Gravitation, 38 p: 1285-1304 ) and (S. Nojiri and S. D. Odintsov, 2017, European Physical Journal C, 77, pp.1-8 ); our current work reports a study on cosmological parameters and thermodynamics with entropy-corrections (logarithmic and power-law) to cosmological horizon entropy as well as black hole entropy with a highly generalized viscous coupled holographic dark fluid along its particular cases.

physics.gen-ph↗

arXiv2024

Reconstruction schemes of scalar field models for the Power Law Entropy Corrected Holographic Dark Energy model with Ricci scalar cut-off

In this work, we examine the cosmological characteristics of the Power Law Entropy Corrected Holographic Dark Energy (PLECHDE) model with infrared (IR) cut-off, which is determined by the curvature parameter $k$, the time derivative of $H$, and the average radius of the Ricci scalar curvature $R$, which varies with the Hubble parameter $H$ squared. We obtain the deceleration parameter $q$ and the Equation of State (EoS) parameter of Dark Energy (DE) $ω_D$. Additionally, we derive the Hubble parameter $H$ and the scale factor $a$ expressions as functions of the cosmic time $t$. Additionally, we examine the limiting scenario that pertains to a flat Dark Dominated Universe. Furthermore, we establish a correspondence between the DE model considered and some scalar fields, in particular the Generalized Chaplygin Gas, the Modified Chaplygin Gas, the Modified Variable Chaplygin Gas, the New Modified Chaplygin Gas, the Viscous Generalized Chaplygin Gas, the Dirac-Born-Infeld, the Yang-Mills, and the Non Linear Electrodynamics scalar field models.

gr-qc↗

arXiv2023

A Non-Linear Type Equation of State and Cosmic Fluid Dynamics

In this chapter we have introduced a special type of non-linear equation of state to discuss the cosmological evolution mechanism. The new equation of state is a four parameters model which can be represented as $p=Aρ+Bρ^2-\frac{C}{ρ^α}$ where $B=Aβ-γ$. The evolution of universe have been interpreted by fluid dynamics. The reconstruction of Chaplygin gas and Van-Der-Waals (VDW) fluid equation of states have been done from the parametric analysis of this new non-linear model. Different cosmological phases like Quintom, Quintessence and warm universe have been discussed here. Finally, we have provided a comparative studies of this model with other non-linear fluid solutions.

gr-qc↗

arXiv2022

Multiple fluid theory of cosmic evolution and its thermodynamic analysis

In this paper we have discussed the modified gravity and scalar field DE model specifically DBI essence model with the analysis of thermodynamics during cosmological evolution. We have used the modified gravity with the form f(R,T)=R+2ΛT in our calculations. The basic aim behind this paper is to discuss a theory that unifies modified gravity with DE models including the solutions of some cosmological problems like thermodynamics energy conditions violation problems, finite time future singularity problems, initial singularity problem, Cosmic inflation problem, decelerated expansion problem, graceful exit problem, reheating problem, bouncing nature problem, phase transformation-spontaneous symmetry breaking problem, negative heat capacity paradox problem and obviously the present day universe problems (Continuously decreasing temperature problem, present day DE dominated expansion problem). We have established the viscous effects (both positive and negative viscosity) in our calculation and discussed the negative-positive viscosity by introducing two special type of energy cycles. Finally, we have discussed the stability conditions for universe evolution through cosmic perturbation and resolved the instability problems. We have also shown the state finder trajectories for both with and without viscous fluid on the basis of our calculations to compare our research with the results of other independent DE models

physics.gen-ph↗

arXiv2021

Thermodynamics and energy condition analysis for Van-Der-Waals EOS without viscous cosmology

In this paper we have studied Van-Der-Waals fluid system with the generalized EOS as as discussed in the recent works of Kremer, G.M [1, 4], Vardiashvili, G [2], Jantsch, R.C [3], Capozziello, S [5]. and are functions of energy density and time that are different for the three types of Van der Waals fluid which are one parameter model, two parameters model and three parameters model. We have studied the changes in the parameters for different cosmic phases. We have also investigated the thermodynamics and the stability conditions for these three models. Finally, we have resolved the finite time future singularity problems

gr-qc↗

arXiv2021

Thermodynamic analysis for Non-linear system (Van-der-Waals EOS) with viscous cosmology

The following paper has been motivated from recent works of Kremer, G.M [1, 4], Vardiashvili, G [2], Jantsch, R.C [3], Capozziello, S [5] on Van-Der-Waals EOS cosmology. The main aim for this paper is to analyze the thermodynamics of a Non-linear system which in this case is Van-Der-Waals fluid EOS [6]. We have investigated the Van-Der-Waals fluid system with the generalized EOS as [8]. The third term signifies viscosity which has been considered as an external parameter that only modifies pressure but not the density of the liquid. The and are the two functions of energy density and time that are different for the 3 types of Vander Waal models namely one parameter model, two parameters model and three parameters model [7, 9]. The value of EOS parameter [6, 10] will show different values for different models. We have studied the changes in the parameters for different cosmic phases [4, 5, 6]. We have also studied the thermodynamics and the stability conditions for the three models while considering viscosity [10, 12, 13, 14]. We have discussed the importance of viscosity [11] for explaining accelerating universe with negative pressure [12]. Finally, we have resolved the finite time future singularity problems [15-20] and discussed the thermodynamics energy conditions [21-31] with those models.

gr-qc↗

arXiv2020

Modified Holographic energy density driven inflation and some cosmological outcomes

Motivated by the work of Nojiri et al. (2019) [S. Nojiri, S. D. Odintsov and E. N. Saridakis, Holographic inflation, Phys. Lett. B 797 (2019) 134829], the present study reports a model of inflation under the consideration that the inflationary regime is originated by a type of holographic energy density. The infrared cutoff has been selected based on the modified holographic model that is a particular case of Nojiri-Odintsov holographic dark energy \cite{odi1} that unifies phantom inflation with the acceleration of the universe on late-time. On getting an analytical solution for Hubble parameter we considered the presence of bulk viscosity and the effective equation of state parameter appeared to be consistent with the inflationary scenario with some constraints. It has also been observed that in the inflationary scenario the contribution of bulk viscosity is not of much significance and its influence is increasing with the evolution of the universe. Inflationary observables have been computed for the model and the slow-roll parameters have been computed. Finally, it has been observed that the trajectories in $n_s - r$ are compatible with the observational bound found by Planck. It has been concluded that the tensor to scalar ratio for this model can explain the primordial fluctuation in the early universe as well.

physics.gen-ph↗

arXiv2020

Cosmology of a generalised version of holographic dark energy in presence of bulk viscosity and its inflationary dynamics through slow roll parameters

The present study reports a reconstruction scheme of a Dark Energy (DE) model with higher order derivative of Hubble parameter, which is a particular case of Nojiri-Odintsov holographic DE [S. Nojiri and S. D. Odintsov, Gen. Relativ. Gravit. 38 (2006) 1285.] that unifies phantom inflation with the acceleration of te universe on late-time. The reconstruction has been carried out in presence of bulk-viscosity, where the bulk-viscous pressure has been taken as a function of Hubble parameter. Ranges of cosmic time $t$ have been derived for quintessence, cosmological constant and phantom behaviour of the equation of state (EoS) parameter. In the viscous scenario, the reconstruction has been carried out in an interacting and non-interacting situations and in both the cases stability against small perturbations has been observed. Finally, the slow roll parameters have been studied and a scope of exit from inflation has been observed. Also, availability of quasi exponential expansion has been demonstrated for interacting viscous scenario and a study through tensor to scalar ratio has ensured consistency of the model with the observational bound by Planck. Alongwith primordial fluctuations the interacting scenario has been found to generate strong dissipative regime.

physics.gen-ph↗

arXiv2019

A look into the cosmological consequences of a dark energy model with higher derivatives of $H$ in the framework of Chameleon Brans-Dicke Cosmology

In this paper, we study some relevant cosmological features of a Dark Energy (DE) model with Granda-Oliveiros cut-off, which is just a specific case of Nojiri-Odintsov holographic DE unifying phantom inflation with late-time acceleration, in the framework of Chameleon Brans-Dicke (BD) Cosmology. Choosing a particular ansatz for some of the quantities involved, we derive the expressions of some important cosmological quantities, like the Equation of State (EoS) parameter of DE $w_D$, the effective EoS parameter $w_{eff}$, the pressure of DE $p_D$ and the deceleration parameter $q$. Moreover, we study the behavior of statefinder parameters $r$ and $s$, of the cosmographic parameters $j$, $s_{cosmo}$, $l$ and $m$ and of the squared speed of the sound $v_s^2$ for both case corresponding to non interacting and interacting Dark Sectors. We also plot the quantities we have derived and we calculate their values for $t\rightarrow 0$ (i.e. for the beginning of the Universe history), for $t\rightarrow \infty$ (i.e. for far future) and for the present time, indicated with $t_0$. The EoS parameters have been tested against various observational values available in the literature.

gr-qc↗

arXiv2018

Localization of Energy-Momentum for a Black Hole Spacetime Geometry with Constant Topological Euler Density

The evaluation of the energy-momentum distribution for a new four-dimensional, spherically symmetric, static and charged black hole spacetime geometry with constant non-zero topological Euler density is performed by using the energy-momentum complexes of Einstein and Møller. This black hole solution was recently developed in the context of the coupled Einstein--non-linear electrodynamics of the Born-Infeld type. The energy is found to depend on the mass $M$ and the charge $q$ of the black hole, the cosmological constant $Λ$ and the radial coordinate $r$, while in both prescriptions all the momenta vanish. Some limiting and particular cases are analyzed, illustrating the rather extraordinary character of the spacetime geometry considered.

gr-qc↗

arXiv2018

An interacting New Holographic Dark Energy in the framework of fractal cosmology

In this paper, we study an interacting holographic dark energy model in the framework of fractal cosmology. The features of fractal cosmology could pass ultraviolet divergencies and also make a better understanding of the universe in different dimensions. We discuss a fractal FRW universe filled with the dark energy and cold dark matter interacting with each other. It is observed that the Hubble parameter embraces the recent observational range while the deceleration parameter demonstrates an accelerating universe and a behavior similar to $Λ$CDM. Plotting the equation of state shows that it lies in phantom region for interaction mode. We use $Om$-diagnostic tool and it shows a phantom behavior of dark energy which is a condition of avoiding the formation of black holes. Finally we execute the StateFinder diagnostic pair and all the trajectories for interacting and non-interacting state of the model meet the fixed point $Λ$CDM at the start of the evolution. A behavior similar to Chaplygin gas also can be observed in statefinder plane. We find that new holographic dark energy model (NHDE) in fractal cosmology expressed the consistent behavior with recent observational data and can be considered as a model to avoid the formation of black holes in comparison with the main model of NHDE in the simple FRW universe. It has also been observed that for the interaction term varying with matter density, the model generates asymptotic de-Sitter solution. However, if the interaction term varies with energy density, then the model shows Big-Rip singularity. Using our modified CAMB code, we observed that the interacting model suppresses the CMB spectrum at low multipoles $l<50$ and enhances the acoustic peaks. Based on the observational data sets used in this paper and using Metropolis-Hastings method of MCMC numerical calculation, ...

gr-qc↗

arXiv2017

Energy-momentum for a charged nonsingular black hole solution with a nonlinear mass function

The energy-momentum of a new four-dimensional, charged, spherically symmetric and nonsingular black hole solution constructed in the context of general relativity coupled to a theory of nonlinear electrodynamics is investigated, whereby the nonlinear mass function is inspired by the probability density function of the continuous logistic distribution. The energy and momentum distributions are calculated by use of the Einstein, Landau-Lifshitz, Weinberg and Møller energy-momentum complexes. In all these prescriptions it is found that the energy distribution depends on the mass $M$ and the charge $q$ of the black hole, an additional parameter $β$ coming from the gravitational background considered, and on the radial coordinate $r$. Further, the Landau-Lifshitz and Weinberg prescriptions yield the same result for the energy, while in all the aforesaid prescriptions all the momenta vanish. We also focus on the study of the limiting behavior of the energy for different values of the radial coordinate, the parameter $β$, and the charge $q$. Finally, it is pointed out that for $r\rightarrow \infty$ and $q = 0$ all the energy-momentum complexes yield the same expression for the energy distribution as in the case of the Schwarzschild black hole solution.

gr-qc↗

arXiv2016

Cosmological reconstruction and {\it Om} diagnostic analysis of Einstein-Aether Theory

In this paper, we will analyse the cosmological models in Einstein-aether gravity, which is a modified theory of gravity in which a time-like vector field breaks the Lorentz symmetry. We will use this formalism to analyse different cosmological models with different behavior of the scale factor. In this analysis, we will use a certain functional dependence of the dark energy on the Hubble parameter. It will be demonstrated that the aether vector field has a non-trivial effect on these cosmological models. We will also perform the \emph{Om} diagnostic in Einstein-aether gravity. Thus, we will fit parameters of the cosmological models using recent observational data.

gr-qc↗

arXiv2016

Israel-Stewart approach to viscous dissipative extended holographic Ricci dark energy dominated universe

This paper reports a study on the truncated Israel-Stewart formalism for bulk viscosity using the extended holographic Ricci dark energy (EHRDE), where the density of dark energy is given as a combination of the Hubble parameter and its derivative. The equations of motion are integrated and the resulting model is analysed under many aspects, including the state finder parameters and the generalised thermodynamics second law. Under the consideration that the universe is dominated by EHRDE the evolution equation for the bulk viscous pressure $Π$ in the framework of the truncated Israel-Stewart theory has been taken as $τ\dotΠ+Π=-3ξH$, where $τ$ is the relaxation time and $ξ$ is the bulk viscosity coefficient. Considering effective pressure as a sum of thermodynamic pressure of EHRDE and bulk viscous pressure it has been observed that under the influence of bulk viscosity the EoS parameter $w_{DE}$ is behaving like phantom i.e. $w_{DE}\leq -1$. It has been observed that the magnitude of the effective pressure $p_{eff}=p+Π$ is decaying with time. We also investigated the case for a specific choice of scale factor namely $a(t)=(t-t_0)^{\fracβ{1-α}}$. For this choice we have observed that a transition from quintessence to phantom is possible for the equation of state parameter. However, the $Λ$CDM phase is not attainable by the statefinder trajectories for this choice. Finally it has been observed that in both of the cases the generalized second law of thermodynamics is valid for the viscous EHRDE dominated universe enveloped by the apparent horizon.

gr-qc↗

arXiv2016

Viscous extended holographic Ricci dark energy in the framework of standard Eckart theory

In the present work we report a study on the viscous extended holographic Ricci dark energy (EHRDE) model under the assumption of existence of bulk viscosity in the linear barotropic fluid and the EHRDE in the framework of standard Eckart theory of relativistic irreversible thermodynamics and it has been observed that the non-equilibrium bulk viscous pressure is significantly smaller than the local equilibrium pressure. We have studied the equation of state (EoS) parameter and observed that the EoS behaves like "quintom" and is consistent with the constraints set by observational data sets from SNLS3, BAO and Planck + WMAP9 + WiggleZ measurements in the reference S. Kumar and L. Xu, \emph{Phys. Lett. B},\textbf{737}, 244 (2014). Analysis of statefinder parameters has shown the possibility of attainment of $Λ$CDM phase under current model and at the same time it has been pointed out that the for $z=0$ i.e. current universe, the statefinder pair is different from that of $Λ$CDM and the $Λ$CDM can be attained in a later stage of the universe. An analysis of stability has shown that although the viscous EHRDE along with viscous barotropic is classically unstable in the present epoch, it can lead to a stable universe in very late stage. Considering an universe enveloped by event horizon we have observed validity of generalized second law of thermodynamics.

gr-qc↗

arXiv2016

Power-Law Entropy-Corrected Holographic Dark Energy in Hořava-Lifshitz Cosmology with Granda-Oliveros Cut-off

In this paper, we study the Power Law Entropy Corrected Holographic Dark Energy (PLECHDE) model in the framework of a non-flat Universe and of Hořava-Lifshitz cosmology with infrared cut-off given by recently proposed Granda-Oliveros cut-off, which contains one term proportional to the Hubble parameter squared $H^2$ and one term proportional to the first time derivative of the Hubble parameter $\dot{H}$. Moreover, this cut-off is characterized by two constant parameters, $α$ and $β$. For the two cases corresponding to non-interacting and interacting DE and Dark Matter (DM), we derive the evolutionary form of the energy density of DE $Ω_D'$, the Equation of State (EoS) parameter of DE $ω_D$ and the deceleration parameter $q$. Using the parametrization of the EoS parameter $ω_D\left(z\right)=ω_0+ω_1 z$, we obtain the expressions of the two parameters $ω_0$ and $ω_1$. We also study the statefinder parameters $\left\{ r,s \right\}$, the snap and lerk cosmographic parameters and the squared speed of the sound $v_s^2$. We also calculate the values of the quantities we study for different values of the running parameter $λ$ and for different set of values of $α$ and $β$.

gr-qc↗