arXiv subjects

İzzet Sakallı

Publications and source records attributed to İzzet Sakallı.

At least 91 records · Page 5Linked to original sources

arXiv2022

Physical Properties of Brane-World Black Hole Solutions via a Confining Potential

In this paper, we consider two brane-world black holes whose solutions are obtained via a confining potential and study their thermodynamical properties. The modified entropies by taking account of the generalized uncertainty principle (GUP) are obtained. We also determine the scalar effective potentials in order to compute the greybody factors of zero-spin particles (bosons) for both geometries. Finally, using the sixth-order WKB approach, quasi-normal modes (QNMs), which are also known as black hole fingerprints, are derived concerning the brane-world black hole parameters. The results obtained are graphically depicted, tabulated, and interpreted.

hep-th↗

arXiv2022

Reply to "Comment on 'Greybody radiation and quasinormal modes of Kerr-like black hole in Bumblebee gravity model' "

In our recent study Ref. [1]: Eur. Phys. J. C 81, 501 (2021) , the main goal was to reveal the Lorentz symmetry breaking (LSB) effect in the rotating black holes via the greybody factor and quasinormal mode analyzes. Ding et al. [2] Kerr-like black hole solution of the bumblebee gravity model used in our paper [1] has unquestionably proven by Maluf and Muniz [3] that it is wrong. We now explain under which condition the greybody factor and quasinormal mode analyzes performed in [1] become valid. We re-make the calculations according to the condition in question and present the new results in this reply.

gr-qc↗

arXiv2022

Greybody Radiation of scalar and Dirac perturbations of NUT Black Holes

We consider the spinorial wave equations, namely the Dirac and the Klein-Gordon equations, and greybody radiation in the NUT black hole spacetime. To this end, we first study the Dirac equation in NUT spacetime by using a null tetrad in the Newman-Penrose (NP) formalism. Next, we separate the Dirac equation into radial and angular sets. The angular set is solved in terms of associated Legendre functions. With the radial set, we obtain the decoupled radial wave equations and derive the one-dimensional Schrödinger wave equations together with effective potentials. Then, we discuss the potentials by plotting them as a function of radial distance in a physically acceptable region. We also study the Klein-Gordon equation to compute the greybody factors (GFs) for both bosons and fermions. The influence of the NUT parameter on the GFs of the NUT spacetime is investigated in detail.

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arXiv2021

GUP modified Hawking Radiation and Transmission/Reflection Coefficients of Rotating Polytropic Black Hole

In this paper, we study the GUP (Generalized Uncertainty Principle) modified Hawking radiation of rotating polytropic black hole given in the Boyer-Lindquist coordinates. To this end, the GUP modified Klein-Gordon equation is applied for investigating the quantum tunneling of scalar particles from the polytropic black hole. After reducing the obtained radial wave equation to the one-dimensional Schrödinger equation, we derive the reflection and transmission probabilities of the radiation. A detail discussion on how the reflection and transmission (greybody factor) probabilities are derived for this black hole is given. The results are graphically depicted and the relevant physical interpretations are made.

hep-th↗

arXiv2021

Quasinormal modes of dS and AdS Black Holes: Feedforward neural network method

In this paper, we show how the quasinormal modes (QNMs) arise from the perturbations of massive scalar fields propagating in the curved background by using the artificial neural networks. To this end, we architect a special algorithm for the feedforward neural network method (FNNM) to compute the QNMs complying with the certain types of boundary conditions. To test the reliability of the method, we consider two black hole spacetimes whose QNMs are well-known: $4D$ pure de Sitter (dS) and five-dimensional Schwarzschild anti-de Sitter (AdS) black holes. Using the FNNM, the QNMs of are computed numerically. It is shown that the obtained QNMs via the FNNM are in good agreement with their former QNM results resulting from the other methods. Therefore, our method of finding the QNMs can be used for other curved spacetimes that obey the same boundary conditions.

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arXiv2021

Greybody Radiation and Quasinormal Modes of Kerr-like Black Hole in Bumblebee Gravity Model

In the framework of the Lorentz symmetry breaking (LSB), we investigate the quasinormal modes (QNMs) and the greybody factors (GFs) of the Kerr-like black hole spacetime obtained from the bumblebee gravity model. In particular, we analyze the scalar and fermionic perturbations of the black hole within the framework of both semi-analytic WKB method and the time domain approach. The impacts of the LSB on the bosonic/fermionic QNMs and GFs of the Kerr-like black hole are investigated in detail. The obtained results are graphically depicted and discussed.

hep-th↗

arXiv2020

Greybody factors of black holes in dRGT massive gravity coupled with nonlinear electrodynamics

In the context of the dRGT massive gravity coupled with nonlinear electrodynamics, we present new dRGT black hole solutions. Together with the thermodynamical properties of the solutions, we study the greybody factor of the corresponding black hole solution. To this end, we compute the rigorous bound on the greybody factor for the obtained dRGT black holes. The obtained results are graphically represented for different values of the theory's physical parameters. Our analysis shows that the charged dRGT black holes of nonlinear electrodynamics evaporate quicker than the charged dRGT black holes originated from linear electrodynamics.

hep-th↗

arXiv2020

Testing Generalized Einstein-Cartan-Kibble-Sciama Gravity using Weak Deflection Angle and Shadow Cast

In this paper, we use a new asymptotically flat and spherically symmetric solution in the generalized Einstein-Cartan-Kibble-Sciama (ECKS) theory of gravity to study the weak gravitational lensing and its shadow cast. To this end, we first compute the weak deflection angle of generalized ECKS black hole using the Gauss-Bonnet theorem in plasma medium and in vacuum. Next by using the Newman-Janis algorithm without complexification, we derive the rotating generalized ECKS black hole and in the sequel study its shadow. Then, we discuss the effects of the ECKS parameter on the weak deflection angle and shadow of the black hole. In short, the goal of this paper is to give contribution to the ECKS theory and look for evidences to understand how the ECKS parameter effects the gravitational lensing. Hence, we show that the weak deflection of black hole is increased with the increase of the ECKS parameter.

gr-qc↗

arXiv2020

Holographic Dissipative Properties of Non-relativistic Black Branes with Hyperscaling Violation

In this work, we consider a class of hyperscaling violating Lifshitz-like black branes with metric scaling components $z=2$ and $θ=-1$ whose corresponding holographic model can be treated as a non-relativistic fluid exhibiting Lifshitz-type symmetry. Having performed analytical calculations via the Klein-Gordon equation and the linear response theory, the experimental realizations of the concerned model, namely the transport coefficients, are found to behave as $η\propto T^{3/2}$, $σ_{DC} \propto T^{3/2}$, and $ρ_{DC} \propto T^{-3/2}$. The associated metric scaling exponents from the bulk theory are encrypted in the transport coefficients obtained for the holographic dual model. We believe that our analytical results can contribute to the endeavours in accomplishing a full understanding on the strongly coupled phenomena occurring in systems such as high temperature superconductors, the hypothetical magnetic monopoles, and liquid crystals.

hep-th↗

arXiv2020

Shadow cast of non-commutative black holes in Rastall gravity

We study the shadow and energy emission rate of a spherically symmetric non-commutative black hole in Rastall gravity. Depending on the model parameters, the non-commutative black hole can reduce to the Schwarzschild black hole. Since the non-vanishing non-commutative parameter affects the formation of event horizon, the visibility of the resulting shadow depends on the non-commutative parameter in Rastall gravity. The obtained sectional shadows respect the unstable circular orbit condition, which is crucial for physical validity of the black hole image model.

hep-th↗

arXiv2020

PV criticality of Achucarro-Ortiz black hole in the presence of higher order quantum and GUP corrections

In this paper, we study quantum-corrected and GUP-(generalized uncertainty principle) corrected thermodynamics of the (2+1)-dimensional charged-rotating Achucarro-Ortiz (AO) black hole. The corrected parameters include temperature, entropy, and heat capacity which help in investigating the instability phases of the AO black hole. We show that AO black hole with small mass possesses unstable regions. However, we reveal that those instabilities can be removed by the GUP corrections. Finally, we also compute the maximum temperature that can be reached by the AO black hole.

gr-qc↗

arXiv2020

Greybody Factors of Holographic Superconductors with $z=2$ Lifshitz Scaling

We study the quasinormal modes and thermal radiation of massless spin-0 field perturbations in the background of four-dimensional (4D) non-Abelian charged Lifshitz black branes with $z=2$ hyperscaling violation, which correspond to systems with superconducting fluctuations. After having an analytical solution to the Klein-Gordon equation, we obtain exact quasinormal modes that are purely imaginary. Therefore, there is no oscillatory behavior in the perturbations that guarantees the mode stability of these solutions. We also study the greybody factors, absorption cross-section, and decay rate of the non-Abelian charged Lifshitz black branes. We derive their analytical expressions and then investigate the correspondence in the strongly coupled dual theory. This study might shed light on the mechanism governing the high-temperature superconductors in condensed matter physics.

hep-th↗

arXiv2019

Solution of Dirac equation and greybody radiation around a regular Bardeen black hole surrounded by quintessence

The exact solutions of the Dirac equation that describe a massive, non-charged particle with spin-(1/2) in the curved spacetime geometry of regular Bardeen black hole surrounded by quintessence (BBHSQ) are investigated. We first derive the Dirac equation in the BBHSQ background using a null tetrad in the Newman-Penrose formalism. Afterward, we separate the Dirac equation into ordinary differential equations for the radial and angular parts. The angular equations are solved exactly in terms of standard spherical harmonics. The radial part equations are transformed into a Schrödinger like differential wave equations with effective potentials. The effect of the quintessence on the regular Bardeen black hole is studied by understanding the physical behavior of the effective potentials. In addition, the potentials are plotted with changing the quintessence parameters, magnetic monopole charge parameter and the frequency of the particle in the physically acceptable regions. Finally, we study the greybody radiation of spin-0 particles from the BBHSQ.

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arXiv2019

Weak gravitational lensing by Kerr-MOG Black Hole and Gauss-Bonnet theorem

The deflection angle of Kerr-MOG black holes is studied for different values of the parameter in modified gravity (MOG). To this end, we employ the Gauss-Bonnet theorem, which was first studied by Gibbons and Werner and then extended by Ono, Ishihara and Asada, who use a generalized optical metric where the deflection of light for an observer and source at finite distance. By using this method, we study the weak gravitational lensing by Kerr-MOG black hole. Our computations show that with an increase in the MOG parameter ($α$), the deflection angle becomes significantly larger than that of Kerr black hole. The results obtained show that MOG effect could be taken into account in the gravitational lensing experiments.

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arXiv2019

GUP Modified Hawking Radiation in Bumblebee Gravity

The effect of Lorentz symmetry breaking (LSB) on the Hawking radiation of Schwarzschild-like black hole found in the bumblebee gravity model (SBHBGM) is studied in the framework of quantum gravity. To this end, we consider Hawking radiation spin-0 (bosons) and spin-$\frac{1}{2}$ particles (fermions), which go in and out through the event horizon of the SBHBGM. We use the modified Klein-Gordon and Dirac equations, which are obtained from the generalized uncertainty principle (GUP) to show how Hawking radiation is affected by the GUP and LSB. In particular, we reveal that, independent of the spin of the emitted particle, GUP causes a change in the Hawking temperature of the SBHBGM. Furthermore, we compute the semi-analytic greybody factors (for both bosons and fermions) of the SBHBGM. Thus, we reveal that LSB is effective on the greybody factor of the SBHBGM such that its redundancy decreases the value of the greybody factor. Our findings are graphically depicted.

hep-th↗

arXiv2019

Spectroscopy of Stringy Black Hole

The Maggiore's method, which evaluates the transition frequency that appears in the adiabatic invariant from the highly damped modes, is used to investigate the entropy/area spectra of the Garfinkle-Horowitz-Strominger black hole (GHS-BH). We compute the resonance modes of the GHS-BH by using the confined scalar waves having high azimuthal quantum number. Although the area and entropy are characterized by the GHS-BH parameters, their quantizations are shown to be independent of those parameters. However, both spectra are equally spaced.

gr-qc↗

arXiv2019

Linear Stability of Mandal-Sengupta-Wadia Black Holes

In this letter, the linear stability of static Mandal-Sengupta-Wadia (MSW) black holes in $(2+1)$-dimensional gravity against circularly symmetric perturbations is studied. Our analysis only applies to non-extremal configurations, thus it leaves out the case of the extremal (2+1) MSW solution. The associated fields are assumed to have small perturbations in these static backgrounds. We then consider the dilaton equation and specific components of the linearized Einstein equations. The resulting effective Klein-Gordon equation is reduced to the Schrödinger like wave equation with the associated effective potential. Finally, it is shown that MSW black holes are stable against to the small time-dependent perturbation

gr-qc↗

arXiv2019

Exact traversable wormhole solution in bumblebee gravity

In this study, we found a new traversable wormhole solution in the framework of a bumblebee gravity model. With these types of models, the Lorentz symmetry violation arises from the dynamics of a bumblebee vector field that is non-minimally coupled with gravity. To this end, we checked the wormhole's flare-out and energy (null, weak, and strong) conditions. We then studied the deflection angle of light in the weak limit approximation using the Gibbons-Werner method. In particular, we show that the bumblebee gravity effect leads to a non-trivial global topology of the wormhole spacetime. By using the Gauss-Bonnet theorem (GBT), it is shown that the obtained non-asymptotically flat wormhole solution yields a topological term in the deflection angle of light. This term is proportional to the coupling constant, but independent from the impact factor parameter. Significantly, we showed that the bumblebee wormhole solutions, under specific conditions, support the normal matter wormhole geometries.

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