arXiv subjects

Vinod Kumar Bhardwaj

Publications and source records attributed to Vinod Kumar Bhardwaj.

24 records · Page 2Linked to original sources

arXiv2022

A new class of holographic dark energy models in LRS Bianchi Type-I

In this paper, we examine the (LRS) Bianchi-type-I cosmological model with holographic dark energy. The exact solutions to the corresponding field equations are obtained by using generalized hybrid expansion law (HEL). The EoS parameter $ω$ for DE is found to be time dependent and redshift dependent and its exiting range for derived model is agreeing well with the current observations. Here we likewise apply two mathematical diagnostics, the statefinder ({r, s}) and $ω_{d}-ω^{'}_{d}$ plane to segregate HDE model from the $ΛCDM$ model. Here the $ω_{d}-ω^{'}_{d}$ diagnostic trajectories is the good tool to classifying the dynamical DE model. We found that our model lies in both thawing region and freezing region. We have also construct the potential as well as dynamics of the quintessence and tachyon scalar field. Some physical and geometric properties of this model along with the physical acceptability of cosmological solution have been discussed in detail.

gr-qc↗

arXiv2021

Evaluation of cosmological models in $f(R, T)$ gravity in different dark energy scenario

In present paper, we search the existence of dark energy scalar field models within in $f(R, T)$ gravity theory established by Harko et al. (Phys. Rev. D 84, 024020, 2011) in a flat FRW universe. The correspondence between scalar field models have been examined by employing new generalized dynamical cosmological term $ Λ(t) $. In this regards, the best fit observational values of parameters from three distinct sets data are applied. To decide the solution to field equations, a scale factor $ a= \left(\sinh(βt)\right)^{1/n} $ has been considered, where $ β$ \& $n $ are constants. Here, we employ the recent ensues ($H_{0}=69.2$ and $q_{0}=-0.52)$ from (OHD+JLA) observation (Yu et al., Astrophys. J. 856, 3, 2018). Through the numerical estimation and graphical assessing of various cosmological parameters, it has been experienced that findings are comparable with kinematics and physical properties of universe and compatible with recent cosmological ensues. The dynamics and potentials of scalar fields are clarified in FRW scenario in the present model. Potentials reconstruction is highly reasonable and shows a periodic establishment and in agreement with latest observations.

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arXiv2021

Statefinder hierarchy model for the Barrow holographic dark energy

In this paper, we have used the state finder hierarchy for Barrow holographic dark energy (BHDE) model in the system of the FLRW Universe. We apply two DE diagnostic tools to determine $ΛBHDE$ model to have various estimations of $\triangle$. The first diagnostic tool is the state finder hierarchy in which we have studied $S^{(1)}_{3}$ $S^{(1)}_{4}$, $S^{(2)}_{3}$ $S^{(2)}_{4}$ and second is the composite null diagnostic (CND) in which the trajectories ( $S^{(1)}_{3} - ε$), ($S^{(1)}_{4}-ε$), ($S^{(2)}_{3}-ε$)($S^{(2)}_{4}-ε$) are discussed, where $ε$ is fractional growth parameter. The infrared cut-off here is taken from the Hubble horizon. Finally, together with the growth rate of matter perturbation, we plot the state finder hierarchy that determines a composite null diagnosis that can differentiate emerging dark energy from $ΛCDM$. In addition, the combination of the hierarchy of the state finder and the fractional growth parameter has been shown to be a useful tool for diagnosing BHDE, particularly for breaking the degeneracy with different parameter values of the model.

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arXiv2021

Barrow HDE model for Statefinder diagnostic in FLRW Universe

We have analyzed the Barrow holographic dark energy (BHDE) in the framework of the flat FLRW Universe by considering the various estimations of Barrow exponent $\triangle$. Here we define BHDE, by applying the usual holographic principle at a cosmological system, for utilizing the Barrow entropy rather than the standard Bekenstein-Hawking. To understand the recent accelerated expansion of the universe, considering the Hubble horizon as the IR cut-off. The cosmological parameters, especially the density parameter ($Ω_{_D}$), the equation of the state parameter ($ω_{_D}$), energy density ($ρ_{_{D}}$) and the deceleration parameter($q$) are studied in this manuscript and found the satisfactory behaviors. Moreover, we additionally focus on the two geometric diagnostics, the statefinder $(r,s)$ and $O_{m}(z)$ to discriminant BHDE model from the $ΛCDM$ model. Here we determined and plotted the trajectories of evolution for statefinder $(r, s)$, $(r,q)$ and $O_{m}(z)$ diagnostic plane to understand the geometrical behavior of the BHDE model by utilizing Planck 2018 observational information. Finally, we have explored the new Barrow exponent $\triangle$, which strongly affects the dark energy equation of state that can lead it to lie in the quintessence regime, phantom regime, and exhibits the phantom-divide line during the cosmological evolution.

gr-qc↗

arXiv2020

Compatibility between the scalar field models of tachyon, $k$-essence and quintessence in $f(R, T)$ gravity

We investigate the behavior of the scalar field in $f (R, T )$ gravity (Harko et al., Phys. Rev. D 84, 024020, 2011) inside the structure of a flat FRW cosmological model, where $R$ and $T$ have their usual meaning. The deterministic solution of FEs has been settled by considering the scale factor $S(t) = t^{m}e^{kt}$, where $m$ and $k$ are positive constant. Here we utilize three ongoing imperatives ($H_{0}=73.8$ and $ q_{0}=-0.73$) from SNe Ia Union observation (Cunha, Phys. Rev. D 79, 047301, 2009); ($H_{0}=73.8$ and $ q_{0}=-0.55$) from Type Ia Supernova (SNIa) observation in joined with (BAO) and (CMB) observation (Giostri et al., J. Cosmol. Astropart. Phys. 03, 027, 2012); and ($H_{0}=69.2$ and $q_{0}=-0.52)$ from (OHD+JLA) observation (Yu et al., Astrophys. J. 856, 3, 2018). We have measured and graphed several cosmological parameters and found that these findings are appropriate in comparison with the universe's physical and kinematic properties and also compatible with ongoing observations. The correspondence between the scalar field models of tachyon, k-essence, and quintessence is investigated by us. Our model explains the potentials and the dynamics of the scalar fields in the FRW universe. The reconstructed potential is very sensible and has a scaling arrangement. Subsequently, our study supports recent observations.

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arXiv2020

RHDE models in FRW Universe with two IR cut-offs with redshift parametrization

In this manuscript, we have researched the cosmic expansion phenomenon in flat FRW Universe through the interaction of the recently proposed R$\grave{e}$nyi holographic dark energy (RHDE). For this reason, we assumed Hubble (H) and Granda--Oliveros (GO) horizons as IR cut-off in the framework of $f(R, T)$ gravity. With this choice for IR cut-off, we can obtain some important cosmological quantities such as the equation of state $ω_{_T}$, energy density $ρ_{_T}$, density parameter $Ω_{_T}$, and pressure $p_{_T}$, which are the function of the redshift $z$. It is observed that in both IR cut-offs the EoS parameter displays quintom-like behaviour for three different values of $δ$. Here we plot these parameters versus redshift $z$ and discuss the consistency of the recent findings. Next, we explore the $ω_{_T}$-$ω_{_T}^{'}$ plane and the stability analysis of the dark energy model by a perturbation method. Our findings demonstrate that the Universe is an accelerating model of rapid growth that is explained by quintom like behaviour.Hence the feasibility of the RHDE model with Hubble and GO cut-off is supported by our model. The results indicate that the IR cut-offs play a significant role in the understanding of the dynamics of the universe.

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