arXiv subjects

O. Gurtug

Publications and source records attributed to O. Gurtug.

At least 19 recordsLinked to original sources

arXiv2026

Quantum Probe to the Higher Dimensional Yang-Mills Singularity

We investigate the quantum nature of naked curvature singularities in Einstein-Yang-Mills (EYM) theory using the Horowitz-Marolf (HM) criterion, which assesses quantum singularities via the evolution of quantum scalar fields. Focusing on timelike singularities in spacetime dimension $ D \geq 5 $, we analyze both pure Yang-Mills and Einstein-Maxwell-Yang-Mills (EMYM) solutions. We then incorporate higher curvature corrections through Gauss-Bonnet (GB) terms. From positivity requirement the expression under square root that arises in GB may create a secondary singularity that shall be scrutinized carefully. Our analysis reveals that while EYM and EMYM spacetimes remain quantum mechanically singular, the inclusion of GB corrections can, in general, render the singularity quantum mechanically regular for specific values of the mass parameter $m$, which is related to the YM charge $Q$ in $ D = 5 $ space-time dimensions. Contrary, for space-time dimension $D \geq 6$, although the outer (secondary) singularity may be healed quantum mechanically for certain values of the mass parameter $m$, the central singularity remains quantum mechanically singular.

gr-qc↗

arXiv2025

Directional Quantum Singularities in Curzon Spacetime

The scalar quantum probe method developed by Horowitz and Marolf is applied to the cylindrically symmetric Curzon solution. The main cause for choosing the Curzon solution is that it is the best known example that exhibits directional singularity. Interestingly the singularity at $r=0$, for the uncharged Curzon spacetime, which is classically very strong with a divergence rate of the order $\frac{1}{r^{10}}$ becomes regular when examined using scalar quantum field. The charged Curzon spacetime, however, due to the emergence of a second singularity off the $r=0$ singularity does not regularize quantum mechanically. All three different charged versions, i.e. electric, magnetic and dyonic share the same feature.

gr-qc↗

arXiv2020

Gravitational Lensing in Rotating and Twisting Universes

Gravitational lensing caused by the gravitational field of massive objects has been studied and acknowledged for a long period of time. In this paper, however, we propose a different mechanism where the bending of light stems from the non-linear interaction of gravitational, electromagnetic and axion waves that creates the high curvature zone in the space-time fabric. The striking distinction in the present study is that in contrast to the convex lensing in the gravitational field of a massive object, hyperbolic nature of the high curvature zone of the background space-time may give rise to concave lensing. Expectedly detection of this kind of lensing becomes possible through satellite detectors.

gr-qc↗

arXiv2020

Quantum Probe of Time-like Naked Singularities for Electrically and Magnetically Charged Black Holes in a Model of Nonlinear Electrodynamics

The time-like naked singularities of the electrically and magnetically charged black hole solutions obtained in a model of nonlinear electrodynamics proposed by Kruglov is investigated within the framework of quantum mechanics. In view of quantum mechanics, the space-time is quantum regular provided that the time evolution of the test quantum wave packet uniquely propagates on an underlying background. Rigorous calculations have shown that when the singularity is probed with specific quantum wave/particle modes, the quantum wave operator turns out to be essentially self-adjoint. Thus, the time evolution of the quantum wave/particle is determined uniquely. In the case of electrically charged black hole background, the unique evolution is restricted to s-wave only. For the two different magnetically charged black hole backgrounds, the time evolution is restricted to different modes for each case.

gr-qc↗

arXiv2020

Gravitational Lensing in a Model of Nonlinear Electrodynamics: The case for electrically and magnetically charged compact objects

This paper aims to investigate the astrophysical applicability of the electrically and magnetically charged black hole solutions obtained in a model of nonlinear electrodynamics proposed by Kruglov (Ann. Phys. Berlin 2017, 529, 170073). Theoretical calculations of the bending angles and gravitational redshifts from the theory of general relativity are studied numerically by using the stellar data of charged compact objects and a hypothetical quark star model. Calculations have revealed that although the theoretical outcomes differ from the linear Maxwell case, the plotted bending angles coincide with the linear case and it becomes hard to identify the effect of nonlinearity. However, the calculation of the redshift has shown that while the increase in the electric field leads to a decrease in the gravitational redshift,the presence of the strong magnetic field contributes to the gravitational redshift in an increasing manner.

gr-qc↗

arXiv2019

Effect of power-law Maxwell field to the gravitational lensing

In this paper, we extend the gravitational bending of light studies in Kottler metrics to comprise nonlinear electrodynamics within the framework of Einstein - power - Maxwell theory. We show that the closest approach distance and the gravitational bending of light are affected from the presence of charge for particular values of the power parameter $k$, which is defined by means of energy conditions. It is shown that the bending angle of light is stronger in the case of a strong electric field, which is the case for $k=1.2$.

gr-qc↗

arXiv2017

Classical and quantum analysis of an Einstein-Scalar solution in $2+1$ dimensions

The classical and quantum properties of a new solution obtained in $2+1$% -dimensional gravity coupled with a real scalar field is analyzed in detail. The considered new solution is a one-parameter generalization of a previously known solution. We investigate the solution classically by calculating exact null and null circular geodesics which correspond to a typical particle probe of the correspondsing black hole spacetime. The solution admitting naked singularity is investigated within the context of quantum mechanics. The timelike naked singularity is probed with spin-zero and spin-half quantum particles. We show that the curvature singularity in the new solution is stronger and hence in general the spacetime remains quantum singular with respect to a quantum particle probe.

gr-qc↗

arXiv2016

Wavy way to the Kerr metric and the quantum nature of its ring singularity

From inherent non-linearity two gravitational waves, unless they are unidirectional, fail to satisfy a superposition law. They collide to develop a new spacetime carrying the imprints of the incoming waves. Same behaviour is valid also for any massless lightlike field. As a result of the violent collision process either a naked singularity or a Cauchy horizon (CH) develops. It was shown by Chandrasekhar and Xanthopoulos (CX) that a particular class of colliding gravitational waves (CGW) spacetime is locally isometric to the Kerr metric for rotating black holes. This relation came to be known as the CX duality. Such a duality can be exploited as an alternative derivation for the Kerr metric as we do herein. Not each case gives rise to a CH but those which do are transient to a black hole state provided stability requirements are met. These classical considerations can be borrowed to shed light on black hole formation in high energy collisions. Their questionable stability and many other sophisticated agenda, we admit that await for a full - fledged quantum gravity. Yet, to add an element of novelty, a quantum probe is sent in the plane $θ=π/2$ to the naked ring singularity of Kerr which develops for the overspinning case $(a>M)$ to test it from a quantum picture. We show that the spatial operator of the reduced Klein-Gordon equation has a unique self-adjoint extension. As a result, the classical Kerr`s ring singularity is healed and becomes quantum regular. Our poetic message of the paper is summarized as Let there be light that collide with might to disperse the night and create holes that are white

gr-qc↗

arXiv2015

Modified Rindler acceleration as a nonlinear electromagnetic effect

The model proposed originally by Mannheim and Kazanas for fitting the shapes of galactic rotation curves has recently been considered by Grumiller to describe gravity of a central object at large distances. Herein we employ the same geometry within the context of nonlinear electrodynamics (NED). Pure electrical NED model is shown to generate the novel Rindler acceleration term in the metric which explains anomalous behaviors of test particles / satellites. Remarkably a pure magnetic model of NED yields flat rotation curves that may account for the missing dark matter. Weak and Strong Energy conditions are satisfied in such models of NED.

gr-qc↗

arXiv2015

Quantum probes of timelike naked singularities in $2+1-$ dimensional power - law spacetimes

The formation of naked singularities in $2+1-$ dimensional power - law spacetimes in linear Einstein-Maxwell and Einstein-scalar theories sourced by azimuthally symmetric electric field and a self-interacting real scalar field respectively, are considered in view of quantum mechanics. Quantum test fields obeying the Klein-Gordon and Dirac equations are used to probe the classical timelike naked singularities developed at $r=0$. We show that when the classically singular spacetimes probed with scalar waves, the considered spacetimes remains singular. However, the spinorial wave probe of the singularity in the metric of a self-interacting real scalar field remains quantum regular. The notable outcome in this study is that the quantum regularity/singularity can not be associated with the energy conditions.

physics.gen-ph↗

arXiv2014

Emergent cosmological constant from colliding electromagnetic waves

In this study we advocate the view that the cosmological constant is of electromagnetic (em) origin, which can be generated from the collision of em shock waves coupled with gravitational shock waves. The wave profiles that participate in the collision have different amplitudes. It is shown that, circular polarization with equal amplitude waves does not generate cosmological constant. We also prove that the generation of the cosmological constant is related to the linear polarization. The addition of cross polarization generates no cosmological constant. Depending on the value of the wave amplitudes, the generated cosmological constant can be positive or negative. We show additionally that, the collision of nonlinear em waves in a particular class of Born-Infeld theory also yields a cosmological constant.

physics.gen-ph↗

arXiv2014

Quantum probes of timelike naked singularities in the weak field regime of $f(R)$ global monopole spacetime

The formation of a naked singularity in $f(R)$ global monopole spacetime is considered in view of quantum mechanics. Quantum test fields obeying the Klein$-$Gordon, Dirac and Maxwell equations are used to probe the classical timelike naked singularity developed at $r=0$. We prove that the spatial derivative operator of the fields fails to be essentially self-adjoint. As a result, the classical timelike naked singularity formed in $f(R)$ global monopole spacetime remains quantum mechanically singular when it is probed with quantum fields having different spin structures. Pitelli and Letelier (Phys. Rev. D 80, 104035, 2009) had shown that for quantum scalar ($spin$ $0$% ) probes the general relativistic global monopole singularity remains intact. For specific modes electromagnetic ($spin$ $1$) and Dirac field ($% spin$ $1/2$) probes, however, we show that the global monopole spacetime behaves quantum mechanically regular. The admissibility of this singularity is also incorporated within the Gubser's singularity conjecture.

hep-th↗

arXiv2013

Rindler Modified Schwarzschild Geodesics

The mysterious attractive constant radial force acted in the past on Pioneer spacecrafts - the so-called Pioneer anomaly - is considered within the context of Rindler acceleration. As an idea this is tempting since it is reminiscent of the cosmological constant. Fortunately the anomalous force acts radially toward the sun so that it differs from the mission of a cosmological constant. Without resorting to the physical source responsible for such a term we investigate the modified Schwarzschild geodesics. The Rindler acceleration naturally affects all massive / massless particle orbits. Stable orbits may turn unstable and vice versa with a finely-tuned acceleration parameter. The overall role of the extra term, given its attractive feature is to provide confinement in the radial geodesics.

gr-qc↗

arXiv2012

Quantum singularities in a model of f(R) Gravity

The formation of a naked singularity in a model of f(R) gravity having as source a linear electromagnetic field is considered in view of quantum mechanics. Quantum test fields obeying the Klein-Gordon, Dirac and Maxwell equations are used to probe the classical timelike naked singularity developed at r=0. We prove that the spatial derivative operator of the fields fails to be essentially self-adjoint. As a result, the classical timelike naked singularity remains quantum mechanically singular when it is probed with quantum fields having different spin structures.

gr-qc↗

arXiv2012

2+1-dimensional electrically charged black holes in Einstein - Power Maxwell Theory

A large family of new black hole solutions in 2+1-dimensional Einstein-Power-Maxwell (EPM) gravity with prescribed physical properties is derived. We show with particular examples that according to the power parameter k of the Maxwell field, the obtained solutions may be asymptotically flat for 1/2 1 in the vanishing cosmological constant limit. We study the thermodynamic properties of the solution with two different models and it is shown that thermodynamic quantities satisfy the first law. The behaviour of the heat capacity indicates that by employing the 1+1-dimensional dilaton analogy the local thermodynamic stability is satisfied.

gr-qc↗

arXiv2011

2+1 dimensional magnetically charged solutions in Einstein - Power - Maxwell theory

We obtain a class of magnetically charged solutions in 2+1 dimensional Einstein - Power - Maxwell theory. In the linear Maxwell limit, such horizonless solutions are known to exist. We show that in 3D geometry, black hole solutions with magnetic charge does not exist even if it is sourced by power-Maxwell field. Physical properties of the solution with particular power k of the Maxwell field is investigated. The true timelike naked curvature singularity develops when k>1 which constitutes one of the striking effects of the power Maxwell field. For specific power parameter k, the occurrence of timelike naked singularity is analysed in quantum mechanical point of view. Quantum test fields obeying the Klein - Gordon and the Dirac equations are used to probe the singularity. It is shown that the class of static pure magnetic spacetime in the power Maxwell theory is quantum mechanically singular when it is probed with fields obeying Klein-Gordon and Dirac equations in the generic case.

gr-qc↗

arXiv2010

Quantum singularities in (2+1) dimensional matter coupled black hole spacetimes

Quantum singularities considered in the 3D BTZ spacetime by Pitelli and Letelier (Phys. Rev. D77: 124030, 2008) is extended to charged BTZ and 3D Einstein-Maxwell-dilaton gravity spacetimes. The occurence of naked singularities in the Einstein-Maxwell extension of the BTZ spacetime both in linear and non-linear electrodynamics as well as in the Einstein-Maxwell-dilaton gravity spacetimes are analysed with the quantum test fields obeying the Klein-Gordon and Dirac equations. We show that with the inclusion of the matter fields; the conical geometry near r=0 is removed and restricted classes of solutions are admitted for the Klein-Gordon and Dirac equations. Hence, the classical central singularity at r=0 turns out to be quantum mechanically singular for quantum particles obeying Klein-Gordon equation but nonsingular for fermions obeying Dirac equation. Explicit calculations reveal that the occurrence of the timelike naked singularities in the considered spacetimes do not violate the cosmic censorship hypothesis as far as the Dirac fields are concerned. The role of horizons that clothes the singularity in the black hole cases is replaced by repulsive potential barrier against the propagation of Dirac fields.

gr-qc↗

arXiv2010

Theorem to generate Einstein-Non Linear Maxwell Fields

We present a theorem in d-dimensional static, spherically symmetric spacetime in generic Lovelock gravity coupled with a non-linear electrodynamic source to generate solutions. The theorem states that irrespective of the order of the Lovelock gravity and non-linear Maxwell (NLM) Lagrangian, for the pure electric field case the NLM equations are satisfied by virtue of the Einstein-Lovelock equations. Applications of the theorem, specifically to the study of black hole solutions in Chern-Simons (CS) theory is given. Radiating version of the theorem has been considered, which generalizes the Bonnor-Vaidya (BV) metric to the Lovelock gravity with a NLM field as a radiating source. We consider also the radiating power - Maxwell source (i.e. $$F_{μν}F^{μν}$^{q},$ $q=$ finely - tuned constant) within the context of Lovelock gravity.

gr-qc↗