arXiv subjects

Taoufik Ouali

Publications and source records attributed to Taoufik Ouali.

At least 19 recordsLinked to original sources

arXiv2026

Black Holes Thermodynamic Topology in Sharma-Mittal Statistics

In this study, we explore the thermodynamic topology of black holes within the Sharma-Mittal entropy framework. Our study covers several black hole solutions, including charged and uncharged black holes in $d$-dimensional, as well as Schwarzschild and Reissner-Nordström black holes. By introducing the Sharma-Mittal entropy characterized by two parameters $δ$ and $R$, we explore how deviations from the standard Boltzmann-Gibbs statistics modify the thermodynamic structure and stability properties of these systems. Using Duan's $Φ$-mapping theory, we compute the corresponding topological numbers and classify black holes into distinct topological categories according to the winding number $W$. Moreover, our analysis shows that, within the Sharma-Mittal formalism, the topological classification is independent of spacetime dimension in the case $d>4$, although dimensions higher than four exhibit distinct features compared to the four-dimensional Schwarzschild and Reissner-Nordström black holes, reveal different behavior of thermodynamic topology under generalized statistics.

gr-qc↗

arXiv2026

RSD constraints on power-law $f(Q)$ gravity using Barboza-Alcaniz and Jassal-Bagla-Padmanabhan parametrizations

We investigate the late-time accelerated expansion of the Universe in power-law $f(Q)$ gravity, $f(Q) = Q + 6γH_0^2 \left(\frac{Q}{Q_0}\right)^n$, combined with two dynamical dark energy parametrizations, Barboza-Alcaniz (BA) and Jassal-Bagla-Padmanabhan (JBP), which allow a smooth evolution of the equation of state beyond the standard constant $ω$ assumption. We derive analytical expressions for the Hubble parameter and the dark energy density, and constrain the model using Pantheon$^+$ Type Ia Supernovae, DESI DR2 Baryon Acoustic Oscillations, and Cosmic Chronometers. Going beyond purely geometrical probes, we incorporate Redshift Space Distortion (RSD) measurements to test the growth of cosmic structures and distinguish modified gravity from General Relativity through the effective Newton's constant. Both parametrizations reproduce the observed late-time acceleration and remain consistent with growth data, with only mild deviations from $Λ$CDM over low and intermediate redshifts. Notably, both configurations yield $G_{\rm eff} < G$, indicating suppressed growth of matter perturbations. These results establish power-law $f(Q)$ gravity with BA and JBP parametrizations as a viable and versatile alternative to $Λ$CDM across both background and perturbative regimes.

physics.gen-ph↗

arXiv2026

Testing $f(Q)$ Gravity with Logarithmic Equation of State Using Latest Cosmological Data

In this paper, we investigate the late-time accelerated expansion of the Universe in power law $f(Q)$ gravity, where a logarithmic dark energy parametrization is considered: $ω_{de}(z)=ω_0+ω_1\ln(1+z)$. This description gives a smooth deviation from a constant equation of state within the complete range of redshifts. We obtain an analytical expression for the Hubble parameter and we use a Markov Chain Monte Carlo to compare the model with the most recent observational data obtained from Pantheon$^+$ Type Ia supernovae, Baryon Acoustic Oscillation measurements from the second data release (DR2) of the Dark Energy Spectroscopic Instrument, and Cosmic Chronometers. We then perform a statistical comparison between our model and the standard $Λ$CDM model using the Akaike Information Criterion and the Bayesian Information Criterion. From our results, we conclude that the use of logarithmic parametrization in the $f(Q)$ gravity model $f(Q)=Q+6γH_0^2\left(\frac{Q}{Q_0}\right)^n$ is a valid and more flexible alternative to standard dark energy models, as it provides a richer phenomenology at low redshifts.

gr-qc↗

arXiv2026

Testing the running vacuum model in light of DESI-DR2 Measurements

Motivated by the fact that quantum effects leave an imprint on the vacuum equation of state, making it depart from the standard cosmological constant relation, $P_{\rm vac}=-ρ_{\rm vac}$, this work investigates generalized running vacuum models (RVMs) by considering a dynamical vacuum equation of state in which the vacuum energy density, $ρ_{\text{vac}}$, evolves as a function of the Hubble parameter, $H$, and its time derivative, $\dot{H}$. This formulation extends previous running vacuum approaches by incorporating a dependence of the vacuum energy density on both, $H^2$ and $\dot{H}$. The corresponding Friedmann equations are derived and analyzed to study their impact on cosmic expansion. The model parameters are constrained through a joint statistical analysis combining the cosmic microwave background shift parameters, DESI-DR2 observations, PantheonPlus type Ia supernovae compilation, and Hubble rate $H(z)$ measurements. Model comparison is performed using information criteria, the Akaike Information Criterion (AIC) and Deviance Information Criterion (DIC), in order to assess the statistical performance of the RVMs relative to the standard $Λ$CDM scenario. The results show that the generalized RVMs provide a good fit to current observations and represent a statistically competitive alternative to the standard $Λ$CDM model. Notably, all three running vacuum formulations yield lower AIC and DIC values than $Λ$CDM, indicating that dynamical running vacuum energy remains a viable cosmological scenario.

physics.gen-ph↗

arXiv2026

Testing the bulk viscosity within the f(R,T) gravity in light of DESI-DR2 observations

We investigate the cosmological implications of the bulk viscosity within the framework of $f(R,T)$ gravity by considering the linear model $f(R,T)=R+2λT$, where $λ$ characterizes the matter--geometry coupling. Assuming a homogeneous and isotropic Friedmann--Lemaître--Robertson--Walker Universe, we derive analytical expressions for the Hubble parameter in two different scenarios: model A, corresponding to a pressureless viscous fluid ($ω=0$), and model B, where the equation of state (EoS) parameter is treated as a free parameter. The cosmological parameters are constrained through a Markov Chain Monte Carlo analysis. The results show that both viscous $f(R,T)$ models provide an excellent description of the current expansion history and remain compatible with the combined observational data. Model A is slightly favored over the standard cosmological model ($Λ$CDM) according to AICc, reflecting the improved fit achieved with only one additional free parameter. In contrast, the BIC continues to favor the simpler $Λ$CDM model owing to its stronger penalty on model complexity. Although model B yields the lowest minimum $χ^2$, the improvement is too small to justify the introduction of an additional free parameter, resulting in a statistical performance comparable to $Λ$CDM according to the AICc but less favorable according to the BIC.

physics.gen-ph↗

arXiv2026

Dark Matter Signatures in Black Hole Thermodynamics and Information Recovery

In this paper, we investigate the thermodynamic properties and information recovery of Schwarzschild and Reissner--Nordstr"om black holes surrounded by perfect fluid dark matter. We show that, while the Bekenstein--Hawking entropy remains unchanged, dark matter significantly modifies the Hawking temperature by introducing a positive contribution that enhances thermal effects, particularly for small black holes. We find that the phase structure is preserved: Schwarzschild black holes remain unstable, whereas Reissner--Nordstr"om black holes exhibit the standard small/large black hole transition, in which small black holes are stable and large black holes are unstable. Furthermore, we demonstrate that dark matter accelerates Hawking evaporation, thereby reducing black hole lifetimes. We further investigate the black hole information loss paradox using the island formula. In the absence of islands, the entanglement entropy of Hawking radiation grows linearly with time and diverges at late times, thereby violating unitarity. By including island contributions, the entanglement entropy of Hawking radiation saturates at twice the Bekenstein--Hawking entropy, reproducing the Page curve and restoring information recovery for both Schwarzschild and Reissner--Nordstr"om black holes surrounded by perfect fluid dark matter. We derive analytical expressions for the Page time and demonstrate that it is directly determined by the thermodynamic parameters of the black hole. Furthermore, we establish a correspondence between thermodynamics and information recovery by showing that the Page time is governed by the Hawking temperature and the event horizon. Finally, we find that the presence of dark matter reduces the Page time, thereby accelerating information recovery.

gr-qc↗

arXiv2026

Cosmological test of a length-preserving biconnection gravity

We investigate the cosmological implications of an extended gravitational framework based on biconnection gravity, constructed from the Schr$\ddot{o}$dinger connection and its dual. In this approach, the difference between the two connections defines the mutual curvature, which encodes the non-Riemannian geometric degrees of freedom, while their symmetric combination reduces to the Levi-Civita connection and hence reproduces general relativity at the background level. Within this setting, we derive the generalized Friedmann equations for a spatially flat Friedmann-Lemaître-Robertson-Walker Universe. The resulting equations contain additional geometric contributions that may naturally encode an effective dark energy sector induced by the biconnection degrees of freedom. We explore this extra dark energy by adopting five commonly used parametrizations, namely B$Λ$CDM, $ω$CDM, Chevallier-Polarski-Linder, Barboza-Alcaniz, and a logarithmic equations of state. These considerations are confronted with recent observational data, including DESI DR2, Pantheon$^+$, and CC observations. Our analysis shows that the four parameterizations enter the acceleration phase at almost the same redshifts and share the same current value of the Hubble rate. Furthermore, the statistical comparison based on the Akaike, Bayesian, and Deviance Information Criterion shows that Barboza-Alcaniz, and logarithmic parameterizations have strong evidence and are competitive with $Λ$CDM. To classify this biconnection gravity in the plethora theoretical models describing the current cosmic acceleration, we examine its implications through cosmographic tools, including the deceleration, jerk, and snap parameters, as well as through the Statefinder analysis and $Om(z)$ diagnostic.

astro-ph.CO↗

arXiv2026

Thermodynamics and information recovery of Schwarzschild AdS black holes in conformal Killing gravity

We study Schwarzschild AdS black holes in conformal Killing gravity, focusing on their thermodynamics and information recovery via the island formula. Treating the cosmological constant as pressure and the conformal Killing gravity parameter as an independent variable, we find that the Bekenstein-Hawking area law holds, while the conformal Killing gravity parameter dramatically affects phase structure. For a positive conformal Killing gravity parameter, black holes admit an extremal limit and exhibit Van der Waals-like criticality with first and second order phase transitions; for a negative conformal Killing gravity parameter, no extremal limit or criticality occurs. Using the island prescription, we show that without islands, the entanglement entropy of Hawking radiation grows unboundedly, violating unitarity, while including islands after Page time restores the Page curve, with late-time entropy saturating at twice the Bekenstein-Hawking value. Page time can be expressed in terms of thermodynamic quantities, displaying critical behavior for positive conformal Killing gravity parameter, whereas in negative conformal Killing gravity small black holes recover information rapidly and large ones more slowly, with pressure reducing Page time. Our results reveal a direct link between black hole thermodynamics, quantum information recovery, and modified gravity.

gr-qc↗

arXiv2026

Gravitational waves production during preheating within GB gravity with monomial coupling

In this paper, we investigate the production of gravitational waves during the preheating era. To achieve this purpose, we consider Gauss-Bonnet inflation model with Power{\textendash}law potential, $V(ϕ)= V_0 ϕ^n$, and monomial Gauss-Bonnet coupling function, $ξ(ϕ)= ξ_0 ϕ^n$. We examine our model by comparing our findings with the current observational data. After that, we study the preheating stage by adopting an approach in which we establish a link between preheating duration, reheating phase and inflationary parameters. This step allows us to benefit from observational constraints imposed on inflation. Furthermore, we examine the production of gravitational waves during preheating epoch connecting the energy density to the preheating duration, $N_{pre}$, and then with the spectral index $n_s$. The generation of gravitational waves during preheating can satisfy observational constraints. In particular, the predicted present-day gravitational-wave energy density, expressed as a function of the scalar spectral index, is consistent with the Planck constraints for the choice of a dimensionless Gauss-Bonnet coupling parameter $α\equiv 4V_{0}ξ_{0}/3 = -1.5\times 10^{-6}$, an effective equation of state parameter $ω= 1/6$, and a preheating efficiency parameter $δ= 10^{5}$.

gr-qc↗

arXiv2026

Reconstruction of the Quintessence Scalar Field Potential Using Gaussian Processes

Recent cosmological observations, including the latest Dark Energy Spectroscopic Instrument (DESI) data releases DR1 and DR2, have renewed interest in the possibility that dark energy may exhibit dynamical behavior rather than being a strict cosmological constant. In this work, we perform a fully model-independent reconstruction of the quintessence scalar field potential using Gaussian Process regression and current Hubble measurements. Instead of assuming a specific functional form for the scalar field potential, we reconstruct the quintessence potential and the corresponding kinetic energy directly from observational data. Our analysis is based on Hubble parameter measurements obtained from cosmic chronometers and the latest high-precision DESI DR2 baryon acoustic oscillation (BAO) data, together with Type Ia supernova data from the Pantheon+ compilation. Gaussian Processes provide a nonparametric and model-independent framework that allows the data to guide the reconstruction. We employ two covariance functions, namely the squared exponential and the Matern ($ν= 9/2$) kernels, in order to assess the sensitivity of the reconstruction to the kernel choice. We further explore the impact of background cosmological assumptions by considering different priors on the matter density and spatial curvature. Finally, we compare the reconstructed scalar field potential with two theoretically motivated benchmark models: a power law potential and an exponential potential. We find that both models remain consistent with the reconstructed potential within the inferred confidence intervals.

astro-ph.CO↗

arXiv2026

Study of the cosmological tensions and DESI-DR2 in the framework of the Little Rip model

We present an analysis that investigates the $H_0$ and $S_8$ tensions by considering a dark energy model. The latter is a late-time model characterized by a future abrupt event known as the Little Rip (LR) model and characterised by one extra parameter, $β$, compared to the standard model, $Λ$CDM. To test this approach, we perform a statistical analysis by the MCMC method using the most recent observational data. We obtain a positive correlation in ($H_0$, $β$) plane. We also note that the Hubble tension is less than $3σ$ when using early measurements, i.e., Cosmic Microwave Background (CMB) data, and when combining it with Baryon Acoustic Oscillation (BAO) data, but it is no longer so when we combine early and late measurements (i.e. PantheonPlus (PP)). In addition, we test the model with DESI-DR2 combined with CMB and recent SNIa measurements. We notice that our model shifts toward the quintessence field. For a complete statistical analysis, we use the Akaike Information Criteria and Bayesian analysis of the evidence. According to Bayes factors, we find that the LR model provides an improved fit only to CMB data.

astro-ph.CO↗

arXiv2026

Timelike Entanglement Entropy of Hawking Radiation

We introduce the concept of timelike entanglement entropy of Hawking radiation as a novel probe of the black hole information paradox. By analytically continuing black hole spacetimes to Euclidean signature, we define timelike correlations that reveal a sequence of timelike Page times at which the entanglement entropy equals the Bekenstein-Hawking entropy. Applying this framework to Schwarzschild, Reissner-Nordström, static higher-dimensional and braneworld solutions, four-dimensional Kerr, and higher-dimensional rotating Myers--Perry black holes, we demonstrate that timelike entanglement exhibits periodic or quasi-periodic behavior, with the recurrence times sensitive to surface gravity, charge, rotation, and spacetime dimensionality. Extremal and near-extremal black holes display effectively frozen thermal oscillations with persistent rotational modulation, reflecting their near-horizon geometries. Unlike conventional approaches based on islands or firewalls, our framework encodes information entirely in the Hawking radiation, preserving unitarity while avoiding violations of horizon smoothness. These results establish timelike entanglement as a robust and physically transparent mechanism for information recovery and provide a versatile tool for exploring quantum gravitational dynamics across a wide range of black hole spacetimes.

gr-qc↗

arXiv2025

Holographic Central Charge Effects on Black Hole Thermodynamics and Quantum Information

In this paper, based on the Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence, we highlight the fundamental role of the holographic central charge in connecting the boundary theory to quantum information, black hole thermodynamics, and the nature of gravity in the bulk. We establish that the large central charge of the boundary conformal field theory corresponds to classical gravity, while a small central charge corresponds to quantum gravity described by Loop Quantum Gravity. In addition, we study the thermodynamic behavior of AdS-Schwarzschild black holes for both large and small central charges. For large central charge, the classical AdS-Schwarzschild black holes have two phases: unstable small black holes and stable large black holes. Conversely, for small central charge, black holes are stable, and their entropy is smaller than that of classical black holes. To explore the influence of the boundary central charge on the information loss paradox, we use the island formula to recover the Page curve. We find that before the Page time, the entanglement entropy of Hawking radiation increases with time, and its slope is determined by the central charge of the boundary theory. After the Page time, the island inside black holes emerges, and the unitarity of black hole evaporation is restored, yielding a constant entropy consistent with the Page curve. This entanglement entropy, i.e. after the Page time, depends on the Bekenstein-Hawking entropy and includes a logarithmic correction related to the central charge.

hep-th↗

arXiv2025

Primordial black holes within Higgs hybrid metric-Palatini approach

In this paper, we investigate the production of primordial black holes (PBHs) during the radiation-dominated era. The collapse of significant density perturbations originating from large primordial scalar fluctuations generated during inflation can lead to the formation of primordial black holes. In our study, we adopt the Higgs hybrid metric-Palatini model as our framework, in which the inflaton field and the Palatini curvature are non-minimally coupled. To achieve our objective, we analyze the behavior of the primordial curvature power spectrum, which exhibits a large enhancement at small scales corresponding to large wavenumbers $k$. Furthermore, we examine the probability of PBHs formation by studying the mass variance, $σ(M_{PBH})$, and the mass fraction of the total energy density collapsing into PBHs, $β(M_{PBH})$. The evolution of both functions is consistent with current observational constraints. Finally, we investigate the abundance of primordial black holes as a dark matter candidate. We found that they can account for the totality or a fraction of the current dark matter content, depending primarily on the values of the coupling constant and the e-folds number.

astro-ph.CO↗

arXiv2025

Holographic Thermodynamics of Higher-Dimensional AdS Black Holes with CFT Rescaling

In this paper, we study the thermodynamic behavior of charged AdS black holes in higher-dimensional spacetimes within the framework of conformal holographic extended thermodynamics. This formalism is based on a novel AdS/CFT dictionary in which the conformal rescaling factor of the boundary conformal field theory (CFT) is treated as a thermodynamic parameter, while Newton's constant is held fixed and the AdS radius is allowed to vary. We explore how variations in the CFT state, represented by its central charge, influence the bulk thermodynamics, phase structure, and stability of black holes in five and six dimensions. Our analysis reveals the emergence of Van der Waals like phase transitions and critical phenomena governed by the central charge. Additionally, we find that the thermodynamic behavior of AdS black holes is affected by the dimensionality of the bulk spacetime, as we compare higher-dimensional black holes to lower-dimensional ones, such as BTZ black holes. These findings provide new insights into the role of boundary degrees of freedom in shaping the thermodynamics of gravitational systems via holography.

hep-th↗

arXiv2025

Testing Gauss-Bonnet Gravity with DESI BAO Data

In the present paper, we observationally constrain f (G) gravity at the background level using Type Ia supernovae from the Pantheon Plus (PP) sample, cosmic chronometer (CC) data, and the recent Baryon Acoustic Oscillation (BAO) measurements released by DESI. For the analysis, we consider two combinations of datasets: (i) PP + CC, and (ii) PP + CC + DESI BAO. In both cases, we determine the best-fit parameters by numerically solving the modified Friedmann equations for two distinct f (G) models, namely the power-law and exponential forms. This is achieved through Markov Chain Monte Carlo (MCMC) simulations. To assess the statistical significance of the f (G) models, we employ both the Akaike Information Criterion (AIC) and the Bayesian Information Criterion (BIC). Our results show that both f (G) models are statistically favored over the standard ΛCDM model. Notably, the exponential model exhibits an additional future transition at redshift closer to -0.1, indicating a possible return to a decelerating phase. This distinctive behavior sets it apart from both the power-law model and the ΛCDM scenario, which predict continued acceleration into the future.

gr-qc↗

arXiv2025

Thermodynamic Topology of Black Holes within Tsallis Statistics

In this paper, we investigate the thermodynamic topology of black holes within the framework of Tsallis statistics. By integrating Tsallis non-extensive statistics with topological thermodynamics, we analyze the local and global stability of various black hole solutions, including Schwarzschild, Reissner-Nordstrom, and higher-dimensional black holes. The introduction of Tsallis entropy, parameterized by the non-extensive parameter delta, results in distinct thermodynamic behaviors depending on its value. Employing Duan's phi-mapping theory, we classify the thermodynamic topology of four-dimensional Schwarzschild black holes and non-charged higher-dimensional black holes into three distinct classes based on their topological number W: stable (W = +1), unstable (W = -1), and critical (W = 0). Additionally, the thermodynamic topology of Reissner-Nordstrom and charged higher-dimensional black holes is categorized into two classes, where W = +1 indicates a stable class and W = 0 represents a less stable class. Our study further demonstrates that the number of dimensions does not affect the topological thermodynamics within the context of non-extensive statistics. This approach provides novel insights into the interplay between Tsallis statistics and black hole thermodynamics, underscoring the pivotal role of topology in understanding black hole physics.

gr-qc↗

arXiv2025

Model-Independent Reconstruction of f(T) Gravity Using Genetic Algorithms

In this paper, we use genetic algorithms, a specific machine learning technique, to achieve a model-independent reconstruction of $f(T)$ gravity. By using $H(z)$ data derived from cosmic chronometers and radial Baryon Acoustic Oscillation method, including the latest Dark Energy Spectroscopic Instrument (DESI) data, we reconstruct the Hubble rate which is the basis parameter for reconstructing $f(T)$ gravity without any assumptions. In this reconstruction process, we use the current value of the Hubble rate, $H_0$, derived by genetic algorithms. The reconstructed $f(T)$ function is consistent with the standard $Λ$CDM cosmology within the 1$σ$ confidence level across a broad temporal range. The mean $f(T)$ curve, adopting a quadratic form, prompts us to parametrize it using a second degree polynomial. This quadratic deviation from the $Λ$CDM scenario is mildly favored by the data.

astro-ph.CO↗