arXiv subjects

H. El Moumni

Publications and source records attributed to H. El Moumni.

At least 37 records · Page 2Linked to original sources

arXiv2021

Black Hole Shadows in M-theory Scenarios

We study the shadows of four dimensional black holes in M-theory inspired models. We first inspect the influence of M2-branes on such optical aspects for non-rotating solutions. In particular, we show that the M2-brane number can control the circular shadow size. This geometrical behavior is distorted for rotating solutions exhibiting cardioid shapes in certain moduli space regions. Implementing a rotation parameter, we analyze the geometrical shadow deformations. Among others, we recover the circular behaviors for a large M2-brane number. Investigating the energy emission rate at high energies, we find, in a well-defined approximation, that the associated peak decreases with the M2-brane number. Moreover, we investigate a possible connection with observations (from Event Horizon Telescope or future devices) from a particular M-theory compactification by deriving certain constraints on the M2-brane number in the light of the $M87^\star$ observational parameters.

hep-th↗

arXiv2020

Deflection Angle and Shadow Behaviors of Quintessential Black Holes in arbitrary Dimensions

Motivated by M-theory/superstring inspired models, we investigate certain behaviors of the deflection angle and the shadow geometrical shapes of higher dimensional quintessential black holes associated with two values of the dark energy (DE) state parameter, being ω=-\frac{1}{3} and ω=-\frac{2}{3}. Concretely, we derive the geodesic equation of photons on such backgrounds. Thanks to the Gauss-Bonnet theorem corresponding to the optical metric, we compute the leading terms of the deflection angle in the so-called weak-limit approximation. After that, we inspect the effect of DE and the space-time dimension d on the calculated optical quantities. Introducing DE via the field intensity c and the state parameter ω, we find that the shadow size and the deflection angle increase by increasing values of the field intensity c. However, we observe that the high dimensions decrease such quantities for ω-models exhibiting similar behaviors. Then, we consider the effect of the black hole charge, on these optical quantities, by discussing the associated behaviors. The present investigation recovers certain known results appearing in ordinary four dimensional models.

gr-qc↗

arXiv2020

Thermal Image and Phase Transitions of Charged AdS Black Holes using Shadow Analysis

We investigate the relations between the black hole shadow and charged AdS black hole critical behaviour in the extended phase space. Using the thermo-shadow formalism built-in [1], we reveal that the shadow radius can be considered as an efficient tool to study thermodynamical black hole systems. Based on such arguments, we build a thermal profile by varying the RN-AdS black hole temperature on the shadow silhouette. Among others, the Van der Waals-like phase transition takes place. This could open a new window on the thermal picture of black holes and the corresponding thermodynamics from the observational point of view.

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arXiv2020

Shadows of 5D Black Holes from String Theory

We study the shadow behaviors of five dimensional (5D) black holes embedded in type IIB superstring/supergravity inspired spacetimes by considering solutions with and without rotations. Geometrical properties as shapes and sizes are analyzed in terms of the D3-brane number and the rotation parameter. Concretely, we find that the shapes are indeed significantly distorted by such physical parameters and the size of the shadows decreases with the brane or "color" number and the rotation. Then, we investigate geometrical observables and energy emission rate aspects.

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arXiv2020

Weak Deflection angle of some classes of non-linear electrodynamics black holes via Gauss-Bonnet Theorem

In this paper, we study the gravitational lensing by some black hole classes within the non-linear electrodynamics in weak field limits. First, we calculate an optical geometry of the non-linear electrodynamics black hole then we use the Gauss-Bonnet theorem for finding deflection angle in weak field limits. The effect of non-linear electrodynamics on the deflection angle in leading order terms is studied. Furthermore, we discuss the effects of the plasma medium on the weak deflection angle.

gr-qc↗

arXiv2020

On Phase Transition Behaviors of Kerr-Sen Black Hole

We investigate phase transitions and critical behaviors of the Kerr-Sen black hole in four dimensions. Computing the involved thermodynamical quantities including the specific heat and using the Ehrenfest scheme, we show that such a black hole undergoes a second-order phase transition. Adopting a new metric form derived from the Gibss free energy scaled by a conformal factor associated with extremal solutions, we calculate the geothermodynamical scalar curvature recovering similar phase transitions. Then, we obtain the scaling laws and the critical exponents, matching perfectly with mean field theory.

hep-th↗

arXiv2020

$f(R)$ Gravity Effects on Charged Accelerating AdS Black Holes using Holographic Tools

We investigate numerically $f(R)$ gravity effects on certain AdS/CFT tools including holographic entanglement entropy and two-point correlation functions for a charged single accelerated Anti-de Sitter black hole in four dimensions. We find that both holographic entanglement entropy and two-point correlation functions decrease by increasing acceleration parameter $A$, matching perfectly with literature. Taking into account the $f(R)$ gravity parameter $η$, the decreasing scheme of the holographic quantities persist. However, we observe a transition-like point where the behavior of the holographic tools change. Two regions meeting at such a transit-like point are shown up. In such a nomination, the first one is associated with slow accelerating black holes while the second one corresponds to a fast accelerating solution. In the first region, the holographic entanglement entropy and two-point correlation functions decrease by increasing the $η$ parameter. However, the behavioral situation is reversed in the second one. Moreover, a cross-comparison between the entropy and the holographic entanglement entropy is presented providing another counter-example showing that such two quantities do not exhibit similar behaviors.

hep-th↗

arXiv2020

Phase Transition of AdS Black hole in Massive Gravity Revisited via New Prescription

We apply the new thermodynamical method proposed initially by Hindi. et al \cite{base} to revisit the phase structure of the AdS black hole in the massive gravity framework. In comparison to the standard thermodynamical method used in literature \cite{mass}, we show that this new technical approach can easily reproduce the critical behavior inherent to this black hole configuration and addresses some of the shortcomings of the standard method. We also show the ability of this new perception to find all possible critical points and regions in which phase transitions occur, an impossible task in the standard method.

hep-th↗

arXiv2020

On Einstein-non linear-Maxwell-Yukawa de-Sitter black hole thermodynamics

We investigate the thermodynamics of the Einstein-non linear-Maxwell-Yukawa black hole solution in de-Sitter spacetime. After presenting the black hole solution and its horizons, we use different thermodynamics points of view to probe the phase structure of such a black hole, ranging from local, global thermodynamics to the effective thermodynamics formalism with two horizons. Our analysis shows that the black hole can undergo a thermal phase transition between an unstable phase and stable phase. These results are consolidated by our proposal of generalizing effective thermodynamics to three horizons black holes. As by product, we find that the effective temperatures behave as an association of ohmic resistances in an electric circuit, which may reveal a possible analogy between the electric and thermodynamic systems.

hep-th↗

arXiv2019

Dark Energy Effects on Charged and Rotating Black Holes

Using canonical typicality method, we reconsider the study of dark energy effects on four dimensional black holes. Concretely, we investigate the associated influences on the spectrum of various black hole backgrounds including the charged and the rotating ones. For such black hole solutions, we first elaborate analytically the corresponding radiation spectrum, the Hawking temperature and the dark information. Then, we discuss and analyze the corresponding findings. This work, recovering the results of the Schwarzschield black hole, confirms that dark energy can be considered as a cooling system surrounding the black holes providing a colder radiation and a slower Hawking radiation process.

hep-th↗

arXiv2019

Phase transitions and geothermodynamics of black holes in dRGT massive gravity

In this paper, we study the thermodynamics and geothermodynamics of spherical black hole solutions in dRGT massive gravity in a new extended phase space. Inspired by the work of Kastor et al. [1], by interpreting the graviton mass as a thermodynamical variable, we propose a first law of thermodynamics which include a mass term and establish a new Smarr Formula. Then, we perform a thermodynamical analysis to reveal the existence of a critical behavior for black holes in dRGT massive gravity with two different critical points through canonical and grand canonical ensembles. To consolidate these results, we make use of the thermodynamical geometry formalism, with the HPEM and the Gibbs free energy metrics, to derive the singularities of Ricci scalar curvatures and show that they coincide with those of the capacities. The effect of different values of the spacetime parameters on the stability conditions is also discussed.

hep-th↗

arXiv2019

Probing correlation between photon orbits and phase structure of charged AdS black hole in massive gravity background

The phase structure of charged Anti-de Sitter black hole in massive gravity is investigated using the unstable circular photon orbits formalism, concretely we establish a direct link between the null geodesics and the critical behavior thermodynamic of such black hole solution. Our analysis reveals that the radius and the impact parameter corresponding to the unstable circular orbits can be used to probe the thermodynamic phase structure. We also show that the latter are key quantities to characterize the order of Van der Waals-like phase transition. Namely, we found a critical exponent around $ δ= 1/2 $. All these results support further that the photon trajectories can be used as a useful and crucial tool to probe the thermodynamic black holes criticality.

hep-th↗

arXiv2018

Anti-de-Sitter-Maxwell-Yang-Mills black holes thermodynamics from nonlocal observables point of view

In this paper, we analyze the thermodynamic properties of the Anti de Sitter black hole in the Einstein-Maxwell-Yang-Mills-AdS gravity (EMYM) via many approaches and in different thermodynamical ensembles (canonical/ grand canonical). First, we give a concise overview of this phase structure in the entropy-thermal diagram for fixed charges then we investigate this thermodynamical structure in fixed potentials ensemble. The Next relevant step is recalling the nonlocal observables such as holographic entanglement entropy and two-point correlation function to show that both observables exhibit a Van der Waals-like behavior in our numerical accuracy and just near the critical line as the case of the thermal entropy for fixed charges by checking Maxwell's equal area law and the critical exponent. In the light of the grand canonical ensemble, we also find a newly phase structure for such a black hole where the critical behavior disappears in the thermal picture as well as in the holographic one.

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arXiv2018

Entanglement Entropy and Phase Portrait of f(R)-AdS Black Holes in the Grand Canonical Ensemble

In this work, we investigate the thermodynamical behavior of charged AdS black holes from $f(R)$ gravity corrections with a constant Ricci scalar curvature in the grand-canonical ensemble. Using the holographic entanglement entropy, we show that the physical observables behave as in the case of the thermal entropy. By performing numerical computations associated with the thermodynamical quantities versus the entanglement entropy, we confirm that the same phase portrait persists in the holographic framework. In the grand-canonical ensemble, the present result supports the former finding which reveals that the charged $f(R)$ AdS black holes behave much like RN-AdS black holes.

hep-th↗

arXiv2018

Joule-Thomson Expansion of RN-AdS Black Holes in $f(R)$ gravity

In this paper, we study Joule-Thomson effects for charged AdS black holes in $f(R)$ gravity. We obtain the inversion temperatures as well as inversion curves, and investigate similarities and differences between van der Waals fluids and charged AdS black holes in $f(R)$ gravity for this expansion. In addition, we determine the position of the inversion point versus different values of the mass $M$, the charge $Q$ and the parameter $b$ for such black hole. At this point, the Joule-Thomson coefficient $μ$ vanishes, an import feature that we used to obtain the cooling-heating regions by scrutinizing the sign of the $μ$ quantity.

gr-qc↗

arXiv2018

Chaos in charged AdS black hole extended phase space

We present an analytical study of chaos in a charged black hole in the extended phase space in the context of the Poincare-Melnikov theory. Along with some background on dynamical systems, we compute the relevant Melnikov function and find its zeros. Then we analyse these zeros either to identify the temporal chaos in the spinodal region, or to observe spatial chaos in the small - large black hole equilibrium configuration. As a byproduct, we derive a constraint on the Black hole charge required to produce chaotic behaviour. To the best of our knowledge, this is the first endeavour to understand the correlation between chaos and phase picture in black holes.

hep-th↗

arXiv2017

More Insight into Microscopic Properties of RN-AdS Black Hole Surrounded by Quintessence via an Alternative Extended Phase Space

In this work we study the phase transition of the charged-AdS black hole surrounded by quintessence via an alternative extended phase space defined by the charge square $Q^2$ and her conjugate $Ψ$, a quantity proportional to the inverse of horizon radius, while the cosmological constant is kept fixed. The equation of state is derived under the form $Q^2=Q^2(T,Ψ)$ and the critical behavior of such black hole analyzed. In addition, we explore the connection between the microscopic structure and Ruppeiner geothermodynamics. We also find that, at certain points of the phase space, the Ruppeiner curvature is characterized by the presence of singularities that are interpreted as phase transitions.

gr-qc↗

arXiv2017

Phase Transition of Charged-AdS Black Holes and Quasinormal Modes : a Time Domain Analysis

In this work we use the quasinormal mode of a massless scalar perturbation to probe the phase transition of the charged-AdS black hole in time profile. The signature of the critical behavior of this black hole solution is detected in the isobaric process. This paper is a natural extension of [1, 2] to the time domain analysis. More precisely, our study shows a clear signal in term of the damping rate and the oscillation frequencies of the scalar field perturbation. We conclude that the quasinormal modes can be an efficient tool to detect the signature of thermodynamic phase transition in the isobaric process far from the critical temperature, but fail to disclose this signature at the critical temperature

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