arXiv subjects

İzzet Sakallı

Publications and source records attributed to İzzet Sakallı.

97 records · Page 6Linked to original sources

arXiv2018

Fermion Clouds Around $z=0$ Lifshitz Black Holes

The Dirac equation is solved in the $z=0$ Lifshitz black hole ($Z0$LBH) spacetime. The set of equations representing the Dirac equation in the Newman-Penrose (NP) formalism is decoupled into a radial set and an angular set. The separation constant is obtained with the aid of the spin weighted spheroidal harmonics. The radial set of equations, which is independent of mass, is reduced to Zerilli equations (ZEs)\ with their associated potentials. In the near horizon (NH) region, these equations solved in terms of the Bessel functions of the first and second kinds arising from the fermionic perturbation on the background geometry. For computing the BQNMs instead of the ordinary quasinormal modes (QNMs), we first impose the purely ingoing wave condition at the event horizon. And then, Dirichlet boundary condition (DBC) and Newmann boundary condition (NBC) are applied in order to get the resonance conditions. For solving the resonance conditions we follow an iteration method. Finally, Maggiore's method (MM) is employed to derive the entropy/area spectra of the $Z0$LBH which are shown to be equidistant.

hep-th↗

arXiv2018

Absorption Cross-Section and Decay Rate of Dilatonic Black Strings

We studied in detail the propagation of a massive tachyonic scalar field in the background of a five-dimensional ($5D$) Einstein--Yang--Mills--Born--Infeld--dilaton black string: the massive Klein--Gordon equation was solved, exactly. Next we obtained complete analytical expressions for the greybody factor, absorption cross-section, and decay-rate for the tachyonic scalar field in the geometry under consideration. The behaviors of the obtained results are graphically represented for different values of the theory's free parameters. We also discuss why tachyons should be used instead of ordinary particles for the analytical derivation of the greybody factor of the dilatonic $5D$ black string.

hep-th↗

arXiv2018

Shadow cast and Deflection angle of Kerr-Newman-Kasuya spacetime

We study the shadow cast or silhouette generated by a Kerr-Newman-Kasuya (KNK) spacetime (rotating dyon black hole). It is shown that in addition to the angular momentum of the black hole, the dyon charge also affects the shadow image of the KNK black hole. Moreover, we analyze the weak gravitational lensing by the KNK black hole by using the Gauss-Bonnet theorem. Finally, we find that extra dyon charge decreases both the deflection angle and shadow of the KNK black hole.

gr-qc↗

arXiv2018

Analytical Solutions in a Cosmic String Born-Infeld-dilaton Black Hole Geometry: Quasinormal Modes and Quantization

Chargeless massive scalar fields are studied in the spacetime of Born-Infeld dilaton black holes (BIDBHs). We first separate the massive covariant Klein-Gordon equation into radial and angular parts and obtain the exact solution of the radial equation in terms of the confluent Heun functions. Using the obtained radial solution, we show how one gets the exact quasinormal modes (QNMs) for some particular cases. We also solve the Klein-Gordon equation in the spacetime of BIDBH with a cosmic string in which we point out the effect of the conical deficit on the BIDBH. The analytical solutions of the radial and angular parts are obtained in terms of the confluent Heun functions. Finally, we study the quantization of the BIDBH. While doing this, we also discuss the Hawking radiation in terms of the effective temperature.

gr-qc↗

arXiv2018

Gravitational lensing by wormholes supported by electromagnetic, scalar, and quantum effects

Wormholes are one of the most interesting topological features in spacetime, offering a rat run between two vastly separated regions of the universe. In this paper, we study the deflection angle of light by wormholes, which are supported by electric charge, magnetic charge, and scalar fields in the weak field limit approximation. To this end, we apply new geometric methods -- the Gauss-Bonnet theorem and the optical geometry -- to compute the deflection angles. We also verify our findings by using the well-known geodesics method. There exists a similarity between the charge and the quantum corrections on a black hole solution, which has been recently discussed in the context of the relativistic Bohmian quantum mechanics. By replacing classical geodesics with Bohmian trajectories, we introduce a new wormhole solution, whose having matter sources and anisotropic pressure supported by Bohmian quantum effects. The problem of fulfillment of the energy conditions of the Morris-Thorne traversable wormhole is also discussed.

gr-qc↗

arXiv2017

Quantum Tunneling and Quasinormal Modes in the Spacetime of Alcubierre Warp Drive

In a seminal paper, Alcubierre showed that Einstein's theory of general relativity appears to allow a super-luminal motion. In the present study, we use a recent eternal-warp-drive solution found by Alcubierre to study the effect of Hawking radiation upon an observer located within the warp drive in the framework of the quantum tunneling method. We find the same expression for the Hawking temperatures associated with the tunneling of both massive vector and scalar particles, and show this expression to be proportional to the velocity of the warp drive. On the other hand, since the discovery of gravitational waves, the quasinormal modes (QNMs) of black holes have also been extensively studied. With this puprpose in mind, we perform a QNM analysis of massive scalar field perturbations in the background of the eternal-Alcubierre-warp-drive (EAWD) spacetime. Our analytical analysis shows that massive scalar perturbations lead to stable QNMs.

gr-qc↗

arXiv2017

Effect of Lorentz Symmetry Breaking on the Deflection of Light in a Cosmic String Spacetime

We investigate the Lorentz symmetry breaking effects (LSBE) on the deflection of light by a rotating cosmic string spacetime in the weak limit approximation. We first calculate the deflection angle by a static cosmic string for a fixed spacelike 4-vector case (FSL) with the corresponding effective-string optical metric using the Gauss-Bonnet theorem (GBT). Then, we focus on a more general scenario, namely we calculate the deflection angle by a rotating cosmic string applying the GBT to Randers effective-string metric. We obtain a significant modification in the deflection angle because of the LSBE parameter. We find a first and second order correction terms due to the global effective topology which are proportional to the cosmic string and LSBE parameter, respectively. Finally, for a fixed time-like 4-vector (FTL) case, we show that the deflection angle is not affetced by LSBE parameter.

gr-qc↗