arXiv subjects

H. El Moumni

Publications and source records attributed to H. El Moumni.

At least 19 recordsLinked to original sources

arXiv2026

Accretion and Neutrino-Motivated Thermal Diagnostics of Thermodynamically Reconstructed Black Holes from Three-Parameter Generalized Entropy

We study accretion and thermal diagnostics motivated by neutrino processes for a static black hole reconstructed from a three-parameter generalized entropy. The construction is thermodynamic by design: the entropy deformation is not mapped to a radial-coordinate redefinition or to a prescribed Reissner--Nordström-like correction. Instead, the generalized entropy fixes the horizon response factor $Ξ_h=dS_G/dS|_{S_h}$. The effective exterior geometry is then reconstructed by requiring its surface-gravity temperature to reproduce the generalized thermodynamic temperature. As a result, the metric preserves the horizon area and the Schwarzschild asymptotics, and reduces smoothly to Schwarzschild when $Ξ_h\to1$. The entropy response is encoded in $λ_G=1/Ξ_{\rm h}-1$, whereas the exterior radial dependence requires an additional localization prescription. The detailed accretion analysis is performed for the power-law family $h(x)=x^{-p}$, with $p\geq2$. Within this reconstruction family, positive $λ_G$ moves the photon sphere and ISCO inward, decreases the critical shadow scale, raises the radiative efficiency, and concentrates the energy release toward the inner disk, while negative $λ_G$ produces the opposite trend. A complementary comparison with exponential and rational localization functions shows that this qualitative ordering is preserved for the profiles tested, although the magnitude of the strong-field shifts remains profile-dependent. Finally, the neutrino-motivated thermal sector ...

gr-qc↗

arXiv2026

Critical Inter-Horizon Thermal Dynamics on the Lukewarm Reissner-Nordström-de Sitter Manifold

We reinterpret the lukewarm sector of four-dimensional Reissner--Nordström--de Sitter black holes as the exact zero-dissipation thermal manifold of an effective two-horizon nonequilibrium system. In the fixed-charge sector, the inter-horizon thermal affinity controls the entropy production and vanishes precisely on the lukewarm branch. The corresponding linearized thermal mode is governed by an exact relaxation coefficient $K_L(ρ)$, with $ρ=r_+/r_c$, and changes stability at the critical ratio \[ ρ_*=\frac{1+\sqrt{3}-\sqrt{2}\,3^{1/4}}{2}\approx 0.4354, \] where the relaxation time diverges as $τ\sim |ρ-ρ_*|^{-1}$. We then encode this critical structure in a minimal Bragg--Williams functional and an Onsager--Machlup action for the effective trajectories of the thermal mode. In this way, the lukewarm branch is promoted from a geometric equal-temperature locus to a critical inter-horizon thermal manifold.

hep-th↗

arXiv2026

Modified Unruh Thermodynamics in Emergent Gravity: Finite Heat Capacity and Rényi Entropy

We show that Jacobson's thermodynamic derivation of Einstein's equations remains valid when local Rindler horizons are treated as finite heat-capacity systems, resolving the unphysical infinite-bath assumption of standard Unruh thermodynamics. The resulting entropy takes the form of Rényi entropy with nonextensivity parameter $λ\sim C^{-1}$, or equivalently, a new "Einstein entropy" that exactly preserves the Einstein equations for all heat capacities. In both cases, the Unruh temperature is modified as \begin{equation*} T_\text{mod}=\frac{\hbarκ}{2π}\left(1+\frac{S}{C}\right), \end{equation*} establishing a universal link between finite-capacity thermodynamics and nonextensive entropy. We further obtain a corrected scalar Einstein equation with an upper bound on horizon energy flux, pointing to testable signatures in heavy-ion collisions, accelerator spin polarization, and analog gravity experiments. These results reinforce the robustness of the emergent-gravity paradigm and connect spacetime dynamics to generalized entropies of quantum information theory.

hep-th↗

arXiv2025

On Rényi Microstructural Aspects of Asymptotically Flat Charged Black Holes: A Novel Duality

We explore the microstructure of asymptotically flat charged black holes through the lens of nonextensive Rényi statistics. A modified form of the Rényi entropy is proposed to incorporate compressibility effects, and geometrothermodynamics is applied within such a framework. Besides, by quantizing the black hole horizon area, we derive a microscopic description in terms of discrete degrees of freedom, with Rényi entropy providing a nonextensive generalization of the Bekenstein-Hawking entropy. We compute the Rényi partition function and probability distribution in the canonical ensemble, highlighting significant deviations from Boltzmann-Gibbs behavior at finite temperature due to nonextensive effects. The black hole undergoes a first-order Van der Waals-like phase transition between small and large configurations, characterized by discontinuities in entropy and latent heat, both of which are shown to depend on the number of area quanta. A critical threshold emerges beyond which the transition becomes athermal. Additionally, we establish a thermodynamic duality between charged-AdS black holes in Boltzmann-Gibbs statistics and charged-flat Rényi black holes, expressed via a conformal transformation of state variables. This duality extends naturally to higher dimensions. Our results provide new insights into the microstructure of black holes.

hep-th↗

arXiv2024

On M87$^$ and SgrA$^$ Observational Constraints of Dunkl Black Holes

In this work, we investigate the optical properties of a new black hole recently obtained from the Dunkl operator formalism involving a relevant parameter denoted by $ξ$. Concretely, we first investigate the shadows, the Lyapunov exponents of unstable nearly bound orbits and the spherically infalling accretion behaviors in terms of such a parameter. Then, we examine the effect of this parameter on the Dunkl black hole deflection angle in vacuum and medium backgrounds by manipulating the Gauss-Bonnet theorem. Exploiting the M87$^*$ and SgrA$^*$ optical bonds, we provide strong constraints on $ξ$ via the falsification mechanism.

gr-qc↗

arXiv2024

Nonextensive Black Hole Thermodynamics from Generalized Euclidean Path Integral and Wick's Rotation

This paper extends the Euclidean path integral formalism to account for nonextensive statistical mechanics. Concretely, we introduce a generalized Wick's rotation from real time $t$ to imaginary time $τ$ such that, $t\rightarrow-i f_α(τ)$, where $f_α$ a differentiable function and $α$ is a parameter related to nonextensivity. The standard extensive formalism is recovered in the limit $α\rightarrow0$ and $f_0(τ)=τ$. Furthermore, we apply this generalized Euclidean path integral to black hole thermodynamics and derive the generalized Wick's rotations given the nonextensive statistics. The proposed formulation enables the treatment of nonextensive statistics on the same footing as extensive Gibbs-Boltzmann statistics. Moreover, we define a universal measure, $η$, for the nonextensivity character of statistics. Lastly, based on the present formalism, we strengthen the equivalence between the AdS-Schwarzschild black hole in Gibbs-Boltzmann statistics and the flat-Schwarzschild black hole within Rényi statistics and suggest a potential reformulation of the $AdS_5$/$CFT_4$ duality.

hep-th↗

arXiv2024

Cosmological Constant Effect on Charged and Rotating Black Hole Shadows

Motivated by recent astrophysical observations, we investigate the shadow behaviors of four dimensional charged rotating black holes with a cosmological constant. This study is made in terms of a reduced moduli space parameterized by the charge and the rotation parameters. For fixed observers, we analyse in some details the shadow behaviors and the corresponding naked singularities of Kerr-Newman and Kerr-Sen four-dimensional black holes in Anti de Sitter backgrounds. Then, a comparative discussion is provided by computing the geometrical observables and the energy emission rate.

gr-qc↗

arXiv2024

A Supersymmetric Suspicion From Accelerating Black Hole Shadows

In light of the Event Horizon Telescope (EHT) images of the supermassive black holes $\textrm{Sgr A}^\star$ and $\textrm{M87}^\star$, we explore a potential supersymmetry suspicion within the observational data. Specifically, we investigate the shadow of a supersymmetric accelerating black hole and compare our findings with observed quantities such as the angular diameter $\mathcal{D}$ and the fractional deviation $\bmδ$. Our analysis reveals a significant alignment between the calculated quantities and the EHT collaboration measurements. This alignment suggests that the features of the black hole shadows observed by the EHT exhibit characteristics consistent with the supersymmetry framework. Our results provide compelling evidence for supersymmetry from a gravitational perspective, which remains absent from the particle physics viewpoint till now.

hep-th↗

arXiv2024

Riemann Surfaces and Winding Numbers of Rényi Phase Structure of Charged-Flat Black Holes

It's widely recognized that the free energy landscape captures the essentials of thermodynamic phase transitions. In this work, we extend the findings of [1] by incorporating the nonextensive nature of black hole entropy. Specifically, the connection between black hole phase transitions and the winding number of Riemann surfaces derived through complex analysis is extended to the Rényi entropy framework. This new geometrical and non-extensive formalism is employed to predict the phase portraits of charged-flat black holes within both the canonical and grand canonical ensembles. Furthermore, we elucidate novel relations between the number of sheets comprising the Riemann surface of the Hawking-Page and Van der Waals transitions and the dimensionality of black hole spacetimes. Notably, these new numbers are consistent with those found for charged-AdS black holes in Gibbs-Boltzmann statistics, providing another significant example of the potential connection between the cosmological constant and the nonextensive Rényi parameter.

hep-th↗

arXiv2024

Thermal chaos of charged-flat black hole via Rényi formalism

Charged-flat black holes in the Rényi extended phase space demonstrate phase structures akin to those of a van der Waals fluid in four-dimensional spacetime and mirror the behaviors of Reissner-Nordstrom-Anti-de-Sitter black holes within the standard Gibbs-Boltzmann extended phase space. This study delves into the dynamics of states initially positioned within the unstable spinodal region of the phase space associated with the charged-flat black hole when subjected to time-periodic thermal perturbations. Our analysis based on the Mel'nikov method reveals that chaos emerges when the $δ$ parameter surpasses a critical threshold, $δ_c$. This critical quantity is dependent on the black hole charge; notably, a larger value of $Q$ impedes the onset of chaos. Furthermore, we examine the effects of space-periodic thermal perturbations on its equilibrium state and find that chaos invariably occurs, irrespective of the perturbation amplitude. Hence, the chaotic dynamics observed in the analysis of charged-flat black holes under Rényi statistics exhibit resemblances to those of asymptotically AdS-charged black holes investigated via the Gibbs-Boltzmann formalism. This serves as yet another example of a potential and significant connection between the cosmological constant and the nonextensivity Rényi parameter.

hep-th↗

arXiv2024

Signatures of the accelerating black holes with a cosmological constant from the $\textrm{Sgr~A}^\star$ and $\textrm{M87}^\star$ shadow prospects

Recently, the Event Horizon Telescope (EHT) achieved the realization of an image of the supermassive black hole $\textrm{Sgr~A}^\star$ showing an angular shadow diameter $\mathcal{D}= 48.7 \pm 7μas$ and the fractional deviation $\mathbfδ = -0.08^{+0.09}_{-0.09}~\text{(VLTI)},-0.04^{+0.09}_{-0.10}~\text{(Keck)}$, alongside the earlier image of $\textrm{M87}^\star$ with angular diameter $ \mathcal{D}=42 \pm 3 μas$, deviation $\mathbfδ=-0.01^{+0.17}_{-0.17}$ and deviations from circularity estimated to be $Δ\mathcal{C}\lesssim 10\%$. In addition, the shadow radii are assessed within the ranges $3.38 \le \frac{r_{\text{s}}}{M} \le 6.91$ for $\textrm{M87}^\star$ and $3.85 \le \frac{r_{\text{s}}}{M} \le 5.72$ as well as $3.95 \le \frac{r_{\text{s}}}{M} \le 5.92$ for $\textrm{Sgr~A}^\star$ using the Very Large Telescope Interferometer (VLTI) and Keck observatories, respectively. These values are provided with $1$-$σ$ and $2$-$σ$ measurements. Such realizations can unveil a better comprehension of gravitational physics at the horizon scale. In this paper, we use the EHT observational results for $\textrm{M87}^\star$ and $\textrm{Sgr~A}^\star$ to elaborate the constraints on parameters of accelerating black holes with a cosmological constant. Concretely, we utilize the mass and distance of both black holes to derive the observables associated with the accelerating black hole shadow. First, we compare our findings with observed quantities such as angular diameter, circularity, shadow radius, and the fractional deviation from the $\textrm{M87}^\star$ data. This comparison reveals constraints within the acceleration parameter and the cosmological constant... Lastly, one cannot rule out the possibility of the negative values for the cosmological constant on the emergence of accelerated black hole solutions within the context of minimal gauged supergravity...

gr-qc↗

arXiv2023

Rényi Topology of Charged-flat Black Hole: Hawking-Page and Van-der-Waals Phase Transitions

In this paper, we extend the proposed setup in [1,2] for finding the topological charges associated with the Hawking-Page and Van-der-Waals transition points as well as equilibrium phases to catch the nonextensive nature of the black hole entropy, Rigorously speaking we incorporate the Rényi statistics formalism in off-shell Bragg-Williams free energy landscape to examine topologically the Hawking-Page phase transition related to the uncharged/charged-flat black hole in grand canonical and the Van-der- Waals transition in the canonical ensemble and where a vortex/anti-vortex structure is found. For this purpose, we introduce three mappings, the $ψ$- and $ξ$-mapping, for phase transitions classification and the $η$-mapping for equilibrium phases classification. We found that Hawking-Page and Van-der-Waals phase transitions belong to different topological classes and exhibit an interplay of total charge values hinting to a possible new correspondence. Our topological study provides further substantiation for a possible conjecture positing a correspondence between the thermodynamic characteristics of black holes in asymptotically flat spacetime using Rényi statistics, and those in asymptotically Anti-de-Sitter spacetime employing Gibbs-Boltzmann statistics.

hep-th↗

arXiv2023

On some phase equilibrium features of charged black holes in flat spacetime via Rényi statistics

Motivated by the nonextensive nature of entropy in gravitational context and the Gauge/Gravity duality, black hole thermodynamics has been attracting intense emphasis in the literature. Along the present work, we investigate some features of the phase structure and critical phenomena of the 4-dimensional charged black holes in asymptotically flat spacetime within the formalism of Rényi statistics. First, we explore the extended phase space via the Rényi statistics approach. Concretely, based on the modified version of the Smarr formula, we recall the equal-area law to remove the oscillatory non-physical region in the $P_R-V$ and $T_R-S_R$ planes. Then, the coexistence curves are determined, as well as the latent heat of phase change. Moreover, we prove that the critical exponent describing the behavior of the order parameter near the critical point is $\frac{1}{2}$, which is consistent with Landau's theory of continuous phase transition. Lastly, we apply the Hamiltonian approach to Rényi thermodynamics which provides a new and solid mathematical basis for the extension of phase space and puts more insight into an expected and profound possible connection between the nonextensivity Rényi parameter $λ$ and the cosmological constant $ Λ$.

gr-qc↗

arXiv2023

Light Behaviors around Black Holes in M-theory

We study the deflection angle and the trajectory of the light rays around black holes in M-theory scenarios. Using the Gauss-Bonnet theorem, we first compute and examine the deflection angle of the light rays near four and seven-dimensional AdS black holes obtained from the M-theory compactifications on the real spheres on $S^7$ and $S^4$, respectively. We discuss the effect of the M-theory brane number and the rotating parameter on such an optical quantity. We then investigate the trajectories of the light rays using the equation of motion associated with $M2$ and $M5$ branes.

hep-th↗

arXiv2022

Evidence for NO violation of the second law in extended black hole thermodynamics

The purpose of the current letter is to give some relevant clarification on the validity of the laws of thermodynamics and the stability of the horizon by scalar field scattering formalism. On the one side, the connection between the energy of the absorbed particle and the change of the enthalpy of the black hole appears to resolve the violation of the second law. On the other side, such connection stipulates a fixed rank of the gauge group $N$ in the boundary conformal field theory which is against the extended phase space spirit, where the cosmological constant is allowed to vary inducing a holographical dually changing of $N$. By recalling the Grand potential, we suggest more stringent conditions under which the second law holds taking into account the missing information about the variation of the cosmological constant ie. the pressure. Our result offers direct evidence of no violation of the second law in the extended phase space.

hep-th↗

arXiv2022

Light Deflection by Rotating Regular Black Holes with a Cosmological Constant

Using the Gauss-Bonnet theorem, we compute and examine the deflection angle of light rays by rotating regular black holes with a cosmological constant. By the help of optical geometries, we first deal with the Hayward black holes with cosmological contributions. Then, we reconsider the study of the Bardeen solutions. We inspect the cosmological constant effect on the deflection angle of light rays. Concretely, we find extra cosmological correction terms generalizing certain obtained findings. Using graphical analysis, we provide a comparative discussion with respect to the Kerr solutions. The results confirm that the non-linear electrodynamic charges affect the space-time geometry by decreasing the deflection angle of light rays by such cosmological black holes.

gr-qc↗

arXiv2022

Light Deflection Angle by Superentropic Black Holes

Motivated by recent works on light deflection and shadow behaviors on AdS geometries, we investigate the deflection angle of light rays by superentropic black holes. Taking appropriate approximations, we first obtain the involved expression. For large values of the impact parameter, we get a specific value being zero for ordinary black holes without AdS backgrounds. Then, we examine and analyze such an optical quantity by providing graphical discussions in terms of a bounded region of the moduli space required by superentropic black hole conditions. Concretely, we study the deflection angle aspects by varying the black hole mass being fixed in the previous findings.

gr-qc↗

arXiv2022

Thermodynamic and Optical Behaviors of Quintessential Hayward-AdS Black Holes

Motivated by Dark Energy (DE) activities, we study certain physical behaviors of the quintessential Hayward-AdS black holes in four dimensions. We generalize some physical properties of the ordinary Hayward AdS black holes without the dark sector. We elaborate a study in terms of the new quantities $c$ and $ω_q$ parametrizing the dark sector moduli space. We investigate the effect of such parameters on certain thermodynamic and optical aspects. To show the quintessential thermodynamic behaviors, we first reconsider the critical properties of ordinary solutions. We find that the equation of state predicts a universal ratio given by $χ_0=\frac{P_cv_c}{T_c}=\frac{27-3\sqrt{6}}{50}$, which is different than the universal one appearing for Van der Waals fluids. Considering the quintessential solutions and taking certain values of the DE state parameter $ω_q$, we observe that the new ratio depends on the DE scalar field intensity $c$. In certain regions of the moduli space, we show that this ratio can be factorized using two terms describing the absence and the presence of the dark sector. Then, we analyze also the DE effect on the heat engines. For the optical aspect, we study the influence of DE on the shadows using one-dimensional real curves. Finally, we discuss the associated energy emission rate, using the dark sector.

hep-th↗