arXiv subjects

Harshna Balhara

Publications and source records attributed to Harshna Balhara.

7 recordsLinked to original sources

arXiv2024

Observational Constraints and Cosmographic Analysis of $f({T},{T}_{G})$ Gravity and Cosmology

We perform observational confrontation and cosmographic analysis of $f(T,T_G)$ gravity and cosmology. This higher-order torsional gravity is based on both the torsion scalar, as well as on the teleparallel equivalent of the Gauss--Bonnet combination, and gives rise to an effective dark-energy sector which depends on the extra torsion contributions. We employ observational data from the Hubble function and supernova Type Ia Pantheon datasets, applying a Markov chain Monte Carlo sampling technique, and we provide the iso-likelihood contours, as well as the best-fit values for the parameters of the power-law model, an ansatz which is expected to be a good approximation of most realistic deviations from general relativity. Additionally, we reconstruct the effective dark-energy equation-of-state parameter, which exhibits a quintessence-like behavior, while in the future the Universe enters into the phantom regime, before it tends asymptotically to the cosmological constant value. Furthermore, we perform a detailed cosmographic analysis, examining the deceleration, jerk, snap, and lerk parameters, showing that the transition to acceleration occurs in the redshift range $ 0.52 \leq z_{tr} \leq 0.89 $, as well as the preference of the scenario for quintessence-like behavior. Finally, we apply the Om

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arXiv2024

The consequence of higher-order curvature-based constraints on $ f(R, L_m) $ gravity

In this investigation, we perform an observational statistical analysis in the theory of $ f(R, L_m) $ gravity. The proposed theoretical model is based on the Ricci scalar's non-linear contribution. We use a distinct parameterization for the deceleration parameter and constrain the model parameters by using various observational data. To determine the best-fit model for the cosmological parameters, we use different observational datasets such as the Hubble Space Telescope, the Pantheon Supernova Survey, the Gold dataset, the Gamma-Ray Burst (GRB), and the Baryon Acoustic Oscillations (BAO). Furthermore, we study the late-time cosmic evolution of the Universe in detail and examine the implications of the constraint values on cosmological parameters. Additionally, we conduct a thorough comparison with the standard cosmological model $ Λ$CDM and other standard models obtained by Odintsov et al. \cite{Odintsov:2023cli, Odintsov:2024lid} to examine the validity of our proposed model in the low-redshift regimes. Finally, we find that the proposed model encapsulates an intriguing transition from early deceleration at high redshift to acceleration at low redshift, a quintessence dark energy scenario, and convergence towards the well-established $ Λ$CDM model in late-time Universe's evolution.

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arXiv2024

New parametrization of the dark-energy equation of state with a single parameter

We propose a novel dark-energy equation-of-state parametrization, with a single parameter $η$ that quantifies the deviation from $Λ$CDM cosmology. We first confront the scenario with various datasets, from Hubble function (OHD), Pantheon, baryon acoustic oscillations (BAO), and their joint observations, and we show that $η$ has a preference for a non-zero value, namely a deviation from $Λ$CDM cosmology is favored, although the zero value is marginally inside the 1$σ$ confidence level. However, we find that the present Hubble function value acquires a higher value, namely $ H_0= 66.624^{+0.011}_{-0.013}~Km~ s^{-1} Mpc^{-1} $, which implies that the $H_0$ tension can be partially alleviated. Additionally, we perform a cosmographic analysis, showing that the universe transits from deceleration to acceleration in the recent cosmological past, nevertheless, in the future, it will not result in a de Sitter phase, since it exhibits a second transition from acceleration to deceleration. Finally, we perform the Statefinder analysis. The scenario behaves similarly to the $ Λ$CDM paradigm at high redshifts, while the deviation becomes significant at late and recent times and especially in the future.

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arXiv2024

EDSFD parametrization in $ f(R,T) $ gravity with linear curvature terms

This paper investigates the flat Friedmann-Lema$\hat{\imath}$tre-Robertson-Walker (FLRW) cosmological model using a suitable parameterization represented as a differential equation concerning the energy density of the scalar field, $ρ_ϕ$, in the context of $f(R,T)$ gravity theory. This parameterization is known as the Energy Density Scalar Field Differential Equation (EDSFD) parametrization. It results in a solution of the Hubble parameter containing four model parameters, namely, $Ω_{m0},Ω_{ϕ0}, H_0,$ and $α$. To constrain the model parameters, $77$ data points from the Hubble dataset, $1048$ points from the Pantheon dataset, and $6$ data points from BAO are used. Using the constrained values, we analyze and compare our model with the standard $Λ$CDM model. The evolution of the physical parameters, which includes the deceleration parameter, density parameter, Equation of State (EoS) for Dark Energy, and $Om(z)$ diagnostic, are discussed.

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arXiv2023

Bouncing cosmology in modified gravity with higher-order curvature terms

A bouncing scenario of a flat homogeneous and isotropic universe is explored by using the reconstruction technique for the power-law parametrization of the Hubble parameter in a modified gravity theory with higher-order curvature and trace of the energy-momentum tensor terms. It is demonstrated that bouncing criteria are satisfied so that the cosmological initial singularity can be avoided. In addition, it is shown that the equation of state parameter crosses the line of the phantom divide. In the present scenario, the universe is filled with perfect fluid around the bouncing point, in which the universe becomes highly unstable and a big bounce can be realized. Furthermore, it is found that extremal acceleration occurs at the bouncing point.

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arXiv2022

A constrained cosmological model in $f(R,L_m)$ gravity

In this article, we study the expanding nature of universe in the contest of $f(R,L_m)$ gravity theory, here $ R $ represents the Ricci scalar and $ L_m $ is the matter Lagrangian density. With a specific form of $ f(R,L_m) $, we obtain the field equations for flat FLRW metric. We parametrize the deceleration parameter in terms of the Hubble parameter and from here we find four free parameters, which are constraints and estimated by using $H(z)$, $Pantheon$, and their joint data sets. Further, we investigate the evolution of the deceleration parameter which depicts a transition from the deceleration to acceleration phases of the universe. The evolution behaviour of energy density, pressure, and EoS parameters shows that the present model is an accelerated quintessence dark energy model. To compare our model with the $ Λ$CDM model we use some of the diagnostic techniques. Thus, we find that our model in $ f(R,L_m) $ gravity supports the recent standard observational studies and delineates the late-time cosmic acceleration.

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arXiv2022

Curvature dominance DE-model in $f(R)$-gravity

We have probed a cosmological model in $f(R)$-gravity, which is a cubic equation in scalar curvature $R$. The terms arise due to nonlinear $f(R)$ function are treated as energy due to curvature inspired geometry. As a result, we find accelerating expansion in the universe, which creates an anti-gravitating negative pressure in it. Some of the physical parameters are solved using numerical methods. The evolution of the model are examined by the latest observational Hubble data (46-data points) and Pantheon data (the latest compilation of SNIa with 40 binned in the redshift range $0.014 \leqslant z \leqslant1.62$). Some important features of the model have been discussed by analyzing the plots of various dynamical parameters. The plots of deceleration parameter $q$ and the Hubble parameter $H$ describe the accelerating expansion in the evolution of the Universe at the present epoch. The transition from deceleration to acceleration for our model is obtained at redshift $z_{tr} \simeq 0.694069$, which is in good agreement with $Λ$CDM. We have also carried out state finder analysis for our model. The analysis of specific features of the model confirms that our model is consistent with $Λ$CDM in late times.

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