arXiv subjects

A. Belhaj

Publications and source records attributed to A. Belhaj.

At least 37 records · Page 2Linked to original sources

arXiv2021

Deflection Light Behaviors by AdS Black Holes

We investigate the behavior of the deflection of light rays by charged and rotating AdS black holes using the Gauss-Bonnet formalism. Taking weak field approximations and certain appropriate limits associated with AdS geometries, we compute and analyze such an optical quantity by varying the involved moduli space parameters. First, we study the charge and the AdS radius effects on the deflection angle of RN-AdS black holes. For small values of the impact parameter $b$, we find that the charge effect is relevant. Precisely, it decreases the deflection angle, while the AdS background one is not. For large values of $b$, however, these optical behaviors have been inverted and the deflection angle becomes an increasing function of the charge. In this way, the cosmological constant effect is remarked to be relevant showing linear variations of the deflection angle. Varying the charge, we find a critical impact parameter value $b_{c}$ where the charge effect is inverted. For rotating solutions, we show that the spinning parameter still decreases the deflection angle without any changing behavior observed in the charge effect. Evincing of the cosmological constant, we recover known results corresponding to charged and rotating ordinary black hole solutions. Examining the plasma effect, we reveal that the deflection angle keeps the same behavior being a decreasing function in terms of the frequency ratio.

hep-th↗

arXiv2021

Superentropic AdS Black Hole Shadows

We study shadow aspects of superentropic black holes in four dimensions. Using Hamilton-Jacobi formalism, we first get the null geodesic equations. In the celestial coordinate framework relying on fixed positions of observers, we investigate the shadow behaviors in terms of the mass and the cosmological scale variation parameters. Among others, we obtain ellipse shaped geometries contrary to usual black hole solutions. Modifying the ordinary relations describing geometrical observables, we discuss the size and the shape deformation parameters of these non-trivial geometric forms. Due to horizonless limits associated with certain mass values, we explore the shadow of the naked singularity of such black holes.

hep-th↗

arXiv2021

On M-theory on Real Toric Fibrations

Borrowing ideas from elliptic complex geometry, we approach M-theory compactifications on real toric fibrations. Precisely, we explore real toric equations rather than complex ones exploited in F-theory and related dual models. These geometries have been built by moving real circles over real bases. Using topological changing behaviors, we unveil certain data associated with gauge sectors relying on affine Lie symmetries.

hep-th↗

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

Dyonic Objects and Tensor Network Representation

Motivated by particle phyiscs results, we investigate certain dyonic solutions in arbitrary dimensions. Concretely, we study the stringy constructions of such objects from concrete compactifications. Then we elaborate their tensor network realizations using multistate particle formalism.

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.

gr-qc↗

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.

hep-th↗

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 Transitions of Quintessential AdS Black Holes in M-theory/Superstring Inspired Models

We study $d$-dimensional $AdS$ black holes surrounded by Dark Energy (DE), embedded in $D$-dimensional M-theory/superstring inspired models having $AdS_d \times \mathbb{S}^{d+k}$ space-time with $D=2d+k$. We focus on the thermodynamic Hawking-Page phase transitions of quintessential DE black hole solutions, whose microscopical origin is linked to $N$ coincident $(d-2)$-branes supposed to live in such $(2d+k)$-dimensional models. Interpreting the cosmological constant as the number of colors $\propto N^{\frac{d-1}{2}}$, we calculate various thermodynamical quantities in terms of brane number, entropy and DE contributions. Computing the chemical potential conjugated to the number of colors in the absence of DE, we show that a generic black hole is more stable for a larger number of branes for lower dimensions $d$.In the presence of DE, we find that the DE state parameter $ω_q$ should take particular values, for $(D,d,k)$ models, providing a non trivial phase transition structure.

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

Stringy Dyonic Solutions and Clifford Structures

Using the toroidal compactification of string theory on n-dimensional tori, Tn, we investigate dyonic objects in arbitrary dimensions. First, we present a class of dyonic black solutions formed by two different D-branes using a correspondence between toroidal cycles and objects possessing both magnetic and electric charges, belonging to %%%% dyonic gauge symmetry. This symmetry could be associated with electrically charged magnetic monopole solutions in stringy model buildings of the standard model extensions. Then, we consider in some details such black hole classes obtained from even dimensional toroidal compactifications, and we find that they are linked to Cl(n) Clifford algebras using the vee product. It is believed that this analysis could be extended to dyonic objects which can be obtained from local Calabi-Yau manifold compactifications.

hep-th↗

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↗

arXiv2017

Four-qubit Systems and Dyonic Black Hole-Black Branes in Superstring Theory

Using dyonic solutions in the type IIA superstring theory on Calabi-Yau manifolds, we reconsider the study of black objects and quantum information theory using string/string duality in six dimensions. Concretely, we relate four-qubits with a stringy quaternionic moduli space of type IIA compactification associated with a dyonic black solution formed by black holes (BH) and black 2-branes (B2B) carrying 8 electric charges and 8 magnetic charges. This connection is made by associating the cohomology classes of the heterotic superstring on T^{4} to four-qubit states. These states are interpreted in terms of such dyonic charges resulting from the quaternionic symmetric space \frac{SO(4,4)}{SO(4)\times SO(4)} corresponding to a N=4 sigma model superpotential in two dimensions. The superpotential is considered as a functional depending on four quaternionic fields mapped to a class of Clifford algebras denoted as Cl_{0,4}. A link between such an algebra and the cohomology classes of T^4 in heterotic superstring theory is also given.

hep-th↗

arXiv2017

Ground state study of a double core-shell dendrimer nanostructure

Based on a dendrimer graph theory, we investigate the ground state phase diagrams of a nanostructure formed by three spins: $σ=1/2$, S=1 and q=3/2. This nanostructure is built on a dendrimer with triangular core geometry. More precisely, we evaluate the effect of different physical parameters including the exchange interactions, the external magnetic and the crystal fields. By varying these parameters, we analytically elaborate the ground state phase diagrams. Concretely, we found that the existence of the crystal field increases the number of stable phases. The total number of possible phases is 24=2x3x4, which are: ($\pm$1/2,$\pm$1,$\pm$3/2), ($\pm$1/2,0,$\pm$3/2), ($\pm$1/2,$\pm$1,$\pm$1/2) and ($\pm$1/2,0,$\pm$1/2). All these phases are found to be stable, expect two special phases: (+1/2,0,-3/2) and (-1/2,0,+3/2), which are masked by the other phases in all the ground state phase diagrams.

cond-mat.stat-mech↗

arXiv2017

Qubit and Fermionic Fock Spaces from Type II Superstring Black Holes

Using Hodge diagram combinatorial data, we study qubit and fermionic Fock spaces from the point of view of type II superstring black holes based on complex compactifications. Concretely, we establish a one-to-one correspondence between qubits, fermionic spaces and extremal black holes in maximally supersymmetric supergravity obtained from type II superstring on complex toroidal and Calabi-Yau compactifications. We interpret the differential forms of the n-dimensional complex toroidal compactification as states of n-qubits encoding information on extremal black hole charges. We show that there are 2^n copies of n-qubit systems which can be split as 2^n=2^{n-1}+2^{n-1}. More precisely, 2^{n-1} copies are associated with even D-brane charges in type IIA superstring and the other 2^{n-1} ones correspond to odd D-brane charges in IIB superstring. This correspondence is generalized to a class of Calabi-Yau manifolds. In connection with black hole charges in type IIA superstring, an n-qubit system has been obtained from a canonical line bundle of n factors of one dimensional projective space \mathbb{CP}^1.

hep-th↗

arXiv2015

On Thermodynamics of AdS Black Holes in M-Theory

Motivated by a recent work on asymptotically AdS_4 black holes in M-theory, we investigate the thermodynamics and thermodynamical geometry of AdS black holes from M2 and M5-branes. Concretely, we consider AdS black holes in AdS_{p+2}\times S^{11-p-2}, where p=2,5 by interpreting the number of M2 (and M5-branes) as a thermodynamical variable. We study the corresponding phase transition to examine their stabilities by calculating and discussing various thermodynamical quantities including the chemical potential. Then, we compute the thermodynamical curvatures from the Quevedo metric for M2 and M5-branes geometries to reconsider the stability of such black objects. The Quevedo metric singularities recover similar stability results provided by the phase transition program.

hep-th↗