arXiv subjects

Umesh Kumar Sharma

Publications and source records attributed to Umesh Kumar Sharma.

26 records · Page 2Linked to original sources

arXiv2020

Reconstruction of quintessence field for the THDE with swampland correspondence in $f(R,T)$ gravity

In the present work, we construct the Tsallis holographic quintessence model of dark energy in $f(R, T)$ gravity with Hubble horizon as IR cut-off. In a flat FRW background, the correspondence among the energy density of the quintessence model with the Tsallis holographic density permits the reconstruction of the dynamics and the potentials for the quintessence field. The suggested Hubble horizon infrared cut-off for the THDE density acts for two specific cases: (i) THDE 1 and (ii) THDE 2. We have reconstructed the Tsallis holographic quintessence model in the region $ω_Λ > -1$ for the EoS parameter for both the cases. In addition, the quintessence phase of the THDE models is analyzed with swampland conjecture to describe the accelerated expansion of the Universe.

physics.gen-ph↗

arXiv2020

Diagnosing the R$\acute{e}$nyi Holographic Dark Energy model in a flat Universe

In this paper, we have examined the R$\acute{e}$nyi holographic dark energy (RHDE) model in the framework of an isotropic and spatially homogeneous flat FLRW (Friedmann- Lema$\hat i$tre-Robertson-Walker) Universe by considering different values of parameter $δ$, where the infrared cut-off is taken care by the Hubble horizon. We examined the RHDE model through the analysis of the growth rate of perturbations and the statefinder hierarchy. The evolutionary trajectories of the statefinder hierarchy $S_3^1$, $S_3^2$ $S_4^1$, $S_4^2$ versus redshift $z$, shows satisfactory behaviour throughout the Universe evolution. One of the favourable appliance for exploring the dark energy models is the CND (composite null diagnostic) $\{ S_3^1 - ε\}$ and $\{ S_4^1 - ε\}$, where the evolutionary trajectories of the $\{ S_3^1 - ε\}$ and $\{ S_4^1 - ε\}$ pair show remarkable characteristics and the departure from $Λ$CDM could be very much assessed.

gr-qc↗

arXiv2020

Exploring the Sharma-Mittal HDE models with different diagnostic tools

In this paper, we have examined the Sharma-Mittal holographic dark energy model (SMHDE) in the framework of an isotropic and spatially homogeneous flat Friedmann-Robertson-Walker(FRW) Universe by considering different values of parameter $δ$ and $R$, where the infrared cut-off is taken care by the Hubble horizon. We examined the SMHDE model through the analysis of Statefinder hierarchy and the growth rate of perturbation. The evolutionary trajectories of the statefinder hierarchy $S_3^1$, $S_3^2$ $S_4^1$, $S_4^2$ versus redshift z, show satisfactory behavior throughout the Universe evaluation. One promising tool for investigating the dark energy models is the composite null diagnostic(CND) $\{ S_3^1 - ε\}$, where the evolutionary trajectories of the $S_3^1 - ε$ pair present different property and the departure from $Λ$CDM could be well evaluated. Additionally, we investigated the dynamical analysis of the model by $ω_{D}-ω^{'}_{D}$ pair analysis.

physics.gen-ph↗

arXiv2020

A new shape function for wormholes in $f(R)$ gravity and General Relativity

In the present work, a new shape function is proposed inside a modified $f(R)$ gravity and General Relativity in wormhole (WH) geometry. The shape function obeyed all the desired conditions of WH geometry. The equation of state (EoS) parameter, anisotropy parameter and the energy conditions are computed. The tangential null energy conditions and the weak energy condition are validated, as well as the radial energy conditions, which demonstrates the nonappearance of exotic matter due to modified gravity allied with such a new proposal.

physics.gen-ph↗

arXiv2019

Traversable Wormholes in $f(R,T)$ Gravity

In the present article, models of traversable wormholes within the $f(R, T)$ modified gravity theory are investigated. We have presented some wormhole models, developed from various hypothesis for the substance of their matter, i.e. various relationships with their components of pressure (lateral and radial). The solutions found for the shape functions of the wormholes produced complies with the required metric conditions. The suitability of solution is examined by exploring null, strong and dominant energy conditions. It is surmised that the normal matter in the throat may pursue the energy conditions yet the gravitational field exuding from the adjusted gravity hypothesis support the appearance of the non-standard geometries of wormholes.

physics.gen-ph↗

arXiv2019

Interacting Tsallis holographic dark energy: Cosmic behaviour, statefinder analysis and $ω_D-ω'_D$ pair in the non-flat universe

The paper explores the interacting Tsallis holographic dark energy (THDE) model in a non-flat universe following an infrared cutoff as the apparent horizon. The equation of state (EoS) and the deceleration parameter of THDE model are determined to understand the cosmological evolution for interacting THDE model in the nonflat universe. By applying the statefinder $(r, s)$ parameter-pairs diagnostic and $ω_D-ω'_D$ pair dynamical analysis for the derived THDE model, we plot the evolutionary trajectories for different cases of Tsallis parameter $δ$ and interaction term $b^{2}$ and also, for spatial curvature $Ω_{k0}= 0, -0.0012$ and $0.0026$ corresponding to flat, open and closed universes, respectively, in the framework of Planck 2018 base cosmology results VI-LCDM observational data.

physics.gen-ph↗

arXiv2019

Tsallis holographic model of dark energy: Cosmic behaviour, statefinder analysis and $ω_D-ω_D'$ pair in the non-flat universe

The paper investigates the Tsallis holographic dark energy (THDE) model in accordance with the apparent horizon as an infrared cut-off, in a non-flat universe. The cosmological evolution of the deceleration parameter and equation of state of THDE model are calculated. The evolutionary trajectories are plotted for the THDE model for distinct values of the Tsallis parameter $δ$ besides distinct spatial curvature contributions, in the statefinder $(r, s)$ parameter-pairs and $ω_{D}-ω^{'}_{D}$ plane, considering the present value of dark energy density parameter $Ω_{D0} $, $Ω_{D0}=0.72$, in the light of $WMAP + eCMB + BAO + H_{0}$ observational data. The statefinder and $ω_{D}-ω^{'}_{D}$ plane plots specify the feature of the THDE and demonstrate the separation between this framework and other models of dark energy.

physics.gen-ph↗

arXiv2017

Bianchi type-I Dust Filled Accelerating Brans- Dicke Cosmology

In this paper, spatially homogeneous and anisotropic Bianchi type-I cosmological models of Brans-Dicke theory of gravitation are investigated. The model represents accelerating universe at present and is considered to be dominated by dark energy. Cosmological constant $Λ$ is considered as a candidate for the dark energy that has negative pressure and is responsible for the present acceleration. The derived model agrees at par with the recent SN Ia observations. We have set BD-coupling constant $ω$ to be ~$40000$, ~seeing the solar system tests and evidences. We have discussed the various physical and geometrical properties of the models and have compared them with the corresponding relativistic models.

physics.gen-ph↗