arXiv subjects

Aatifa Bargach

Publications and source records attributed to Aatifa Bargach.

6 recordsLinked to original sources

arXiv2025

Spacetime Foam Effects on Charged AdS Black Hole Thermodynamics

In this paper, we investigate the emergent thermodynamic phenomena arising from spacetime foam and its impact on black hole behavior. Within this framework, we adopt the Barrow model, where the structure of spacetime at small scales is modeled by analogy with the Koch snowflake, implying that black hole surfaces acquire a quasi-fractal structure due to quantum deformations induced by quantum gravity effects. Our analysis, conducted within the extended phase-space formalism, reveals that the quasi-fractal correction to black hole entropy significantly modifies the equation of state, critical parameters, and phase-transition behavior of charged AdS black holes. An increase in the Barrow parameter leads to higher critical pressure and temperature, which diverge at maximal deformation. Moreover, while the quasi-fractal structure has a negligible effect on small black holes with low entropy, it clearly influences the thermal evolution of medium and large event horizon black holes. Additionally, we study the impact of quasi-fractal corrections on the Joule-Thomson expansion and the phase transition between cooling and heating regimes. We also examine the effects of spacetime structure on black hole microstate density, lifetimes, and temperature detection by different observers, including local, asymptotic, and Unruh detectors. We find that spacetime foam increases microstate density and prolongs evaporation lifetimes, thus acting as a resistance to black hole evaporation, while local observers experience that the expected Tolman blueshift and Unruh temperatures remain unmodified.

hep-th↗

arXiv2024

Constraints on the reheating phase after Higgs inflation in the hybrid metric-Palatini approach

In this paper, we study the post-inflationary era called reheating stage. For this purpose, we consider a model in which the inflaton is non-minimally coupled to the curvature within the hybrid metric-Palatini approach. Furthermore, to investigate the consistency of our results with the observational data, we relate reheating parameters to those of inflation model. By taking into consideration the Higgs potential $V(ϕ)=λ/4 ϕ^4$; we derive the necessary quantities needed to obtain the reheating duration and the reheating temperature. Moreover, we plot reheating e-folds and temperature as a function of the spectral index, respectively. We consider three cases depending on the coupling constant $ξ$. In addition, we use some specific values of the effective equation of state $ω$, which is presumed to remain relatively constant within the range of $-\frac{1}{3} \leq ω< \frac{1}{3}$. We find that for $ξ=10^{-4.1}$ our results are in agreement with the recent Planck data as the reheating instant is corresponding to the central value of the spectral index and to a maximum temperature required by the scale of baryogenesis models.

gr-qc↗

arXiv2024

Higgs inflation model with non-minimal coupling in hybrid Palatini approach

The inflation model with non-minimal coupling scalar field in the context of the hybrid metric Palatini is studied in this paper. We derive the Einstein's field equations, the equations of motion of the scalar field. Furthermore,the background and the perturbative parameters are obtained by means of Friedmann equation in the slow roll regime. The analysis of cosmological perturbations allowed us to obtain the main inflationary parameters such as the scalar spectral index $n_s$ and the tensor to scalar ratio $r$. In this perspective, as an application of our analysis, we consider the Higgs field with quartic potential which plays the inflaton role, and we show that the predictions of Higgs hybrid inflation are in good agreement with recent observational data \cite{Akrami:2018odb}.

gr-qc↗

arXiv2020

Non-minimal Higgs inflation within holographic cosmology

We derive a Higgs inflationary model in the context of holographic cosmology, where we consider a universe filled with a Higgs field non-minimally coupled to gravity in a slow-roll regime. The amplitude of density (scalar) perturbations is calculated. In this regard, we show that the background and perturbative parameters characterising the inflationary era are related to the standard one through corrections terms. We found that for the e-fold number $N\sim 58$, the spectral index,$n_{r}$, and the tensor-to-scalar ratio,$r$, values are $0.965$ and $0.021$, respectively, which are in agreement with 2018 Planck observational data. However, as soon as we move from $N\sim 58$, the model is ruled out by the current data.

gr-qc↗

arXiv2019

Induced gravity effect on inflationary parameters in an holographic cosmology

We investigate observational constraints on inflationary parameters in the context of an holographic cosmology with an induced gravity correction. We consider two situations where a universe is firstly filled with a scalar field and secondly with a tachyon field. Both cases are investigated in a slow-roll regime. We adopt a quadratic potential and an exponential potential for the scalar and the tachyon inflation respectively. In this regard, the standard background and perturbative parameters characterizing the inflationary era are modified by correction terms. We show a good agreement between theoretical model parameters and Planck2018 observational data for both scalar and tachyon fields.

hep-th↗

arXiv2018

Dynamical system approach of non-minimal coupling in AdS/CFT cosmology

We study the dynamical system approach of non minimally coupled scalar field to induced gravity on the brane in the framework of the AdS/CFT correspondence. In this context, we derive the modified Friedmann equation and the equation of motion. The dynamics of this model are studied by rewriting the cosmological field equations in the form of a system of autonomous differential equations. In particular, the analysis is considered by investigating an exponential potential and a monomial form of the non minimal coupling function. We show that, for sufficient conditions, a past de Sitter attractor solution is obtained in the case of a minimal coupling, meanwhile a future de Sitter attractor solutions is obtained for a conformal coupling and for a non minimal coupling.

hep-th↗