arXiv subjects

E. I. Hassan

Publications and source records attributed to E. I. Hassan.

4 recordsLinked to original sources

arXiv2025

Modified cosmology in $f(Q, L_m)$ gravity

In this letter, we investigate cosmology within the framework of modified $f(Q, L_m)$ gravity using the non-linear model $f(Q, L_m) = -Q + αL_m^n + β$, where $α$, $β$, and $n$ are free parameters. The modified Friedmann equations are derived for a matter-dominated universe, and an analytical solution is obtained. Using Hubble, Pantheon+, and joint datasets, we constrain the model parameters and examine their implications. The results indicate that the model accommodates varying $H_0$ values, contributing to the Hubble tension, while $n \neq 1$ suggests deviations from general relativity (GR). The deceleration parameter confirms a transition to acceleration at $z_t \approx 0.6 - 0.8$, with present values supporting cosmic acceleration. This model offers a viable alternative to GR-based cosmology.

astro-ph.CO↗

arXiv2023

Square-Root parametrization of dark energy in $f(Q)$ cosmology

This paper is a parametrization of the equation of state (EoS) parameter of dark energy (DE), which is parameterized using Square-Root (SR) form i.e. $ω_{SR}=\text{$ω_{0}$}+\text{$ω_{1}$}\frac{z}{\sqrt{z^{2}+1}}$, where $ω_{0}$ and $ω_{1}$ are free constants. This parametrization will be examined in the context of the recently suggested $f(Q)$ gravity theory as an alternative to General Relativity (GR), in which gravitational effects are attributed to the non-metricity scalar $Q$ with the functional form $f(Q)=Q+αQ^{n}$, where $α$ and $n$ are arbitrary constants. We derived observational constraints on model parameters using the Hubble dataset with 31 data points and the Supernovae (SNe) dataset from the Pantheon samples compilation dataset with 1048 data points. For the current model, the evolution of the deceleration parameter, density parameter, EoS for DE, and $Om(z)$ diagnostic have all been investigated. It has been shown that the deceleration parameter favors the current accelerated expansion phase. It has also been shown that the EoS parameter for DE has a quintessence nature at this time.

astro-ph.CO↗

arXiv2023

Impact of dark energy on the equation of state in light of the latest cosmological data

We reconstruct the effective Equation of State (EoS) within the framework of General Relativity (GR) theory in a homogeneous and isotropic FLRW Universe, which is assumed to be composed of matter and Dark Energy (DE). Our analysis employs a dataset consisting of 31 Cosmic Chronometer (CC) data points, six data points of Baryon Acoustic Oscillations (BAO), and 1048 Type Ia Supernovae (SN) from the Pantheon sample, and we determine the best-fit values of the model parameters through Markov Chain Monte Carlo (MCMC) simulation. We then use these parameter values to calculate various cosmological parameters, such as the DE EoS parameter, the energy density, the deceleration parameter, the state finder parameters, and the $Om(z)$ diagnostic. All the analyzed cosmological parameters show behavior consistent with the accelerated Universe scenario.

gr-qc↗

arXiv2023

Constraining the $f(R,T) = R + 2λT$ cosmological model using recent observational data

In this paper, we consider a comprehensive investigation of the cosmological model described by $f(R,T) = R + 2λT$ (where $λ$ represents a free parameter) in light of the most recent observational data. By constraining the model using $Hubble$ and $Pantheon$ datasets, we determine its compatibility with the observed behavior of the Universe. For this purpose, we adopt a parametric form for the effective equation of state (EoS) parameter. This parametric form allows us to describe the evolution of the EoS parameter with respect to redshift and investigate its behavior during different cosmic epochs. The analysis of the deceleration parameter reveals an accelerating Universe with a present value of $q_0=-0.64^{+0.03}_{-0.03}$, indicating the current phase of accelerated expansion. The transition redshift is found to be $z_{tr}=0.53^{+0.04}_{-0.03}$, marking the epoch of transition from deceleration to acceleration. We also analyze the evolution of important cosmological parameters including density parameter, pressure, effective EoS, and stability. These findings collectively demonstrate the viability of the $f(R,T)$ cosmological model as a robust candidate capable of engendering the requisite negative pressure, thereby efficiently propelling cosmic expansion. Moreover, the undertaken stability analysis underscores the model's stability within the broader cosmic landscape. By providing the best-fit values for the coupling parameter $λ$, this approach motivates and encourages further explorations into the extensive landscape of this model and its potential applications across diverse realms of cosmology and astronomy.

astro-ph.CO↗