arXiv subjects

Bekir Can Lütfüoğlu

Publications and source records attributed to Bekir Can Lütfüoğlu.

28 records · Page 2Linked to original sources

arXiv2025

Gravitational Spectra and Wave Propagation in Regular Black Holes Supported by a Dehnen Halo

We investigate gravitational perturbations, quasinormal modes, grey-body factors, and absorption cross-sections of the recently proposed regular and asymptotically flat black hole supported by a Dehnen-type dark-matter halo. This geometry provides a remarkably simple analytic model of supermassive black holes embedded in galactic environments, having a lapse function $ f(r)=1-2 M r^{2}/(r+a)^{3}, $ [R. A. Konoplya, A. Zhidenko, 2511.03066]. The regularizing parameter $a$ is the characteristic scale of the halo. We compute the quasinormal spectrum for both axial "up" and "down" perturbations using the WKB method and verify the results through time-domain integration. The two sectors are no longer isospectral, and the deviations grow with the halo scale parameter. The grey-body factors and absorption cross-sections are extracted via standard scattering boundary conditions and the WKB approach, and their behaviour is fully consistent with the structure of the effective potentials. Altogether, our analysis demonstrates that a dark-matter halo imprint induces modifications in the gravitational response, while the employed approximation schemes remain sufficiently accurate for quantitative predictions. At asymptotically late times, the presence of the halo does not alter the Price-law decay, which remains identical to that of a Schwarzschild black hole in vacuum.

gr-qc↗

arXiv2025

Proper-Time Approach in Asymptotic Safety via Black Hole Quasinormal Modes and Grey-body Factors

We study the quasinormal mode spectrum and grey-body factors of black holes in an effectively quantum-corrected spacetime, focusing on the influence of near-horizon modifications on observable quantities. Employing scalar, electromagnetic, and Dirac test fields, we analyze the perturbation equations and extract the fundamental quasinormal frequencies using both the 6th-order WKB method with Padé resummation and time-domain integration. Our results show that quantum corrections near the horizon significantly affect the real and imaginary parts of the quasinormal modes, particularly for low multipole numbers and in the near-extremal regime. We also verify the robustness of the correspondence between quasinormal modes and grey-body factors by comparing WKB results with those reconstructed from the dominant quasinormal modes. Across all field types and parameter ranges considered, the WKB method proves accurate within a few percent, confirming its reliability in probing the impact of near-horizon physics. These findings support the use of quasinormal ringing and Hawking radiation spectra as sensitive tools for testing quantum modifications of black hole spacetimes.

gr-qc↗

arXiv2025

Thermodynamics of the Reissner-Nordström black hole with quintessence matter on the EGUP framework

In this paper, we investigate the quantum correction on thermodynamics of the Reissner-Nordström black hole in the presence of the quintessence matter associated with dark energy. To this end, the modified Hawking temperature, heat capacity, and entropy functions of the black hole are derived. { Investigation reveals that the modified uncertainty principles and normalization factor $α$ restrict the lower bound value of horizon radius to affect the Hawking temperature and the parameter $η_{0}$ have a non-negligible effect on the heat capacity threshold.} {Furthermore}, the correction of entropy does not depend on the quintessence matter. It is also examined the equation of state associated with the pressure and the volume in this framework. In addition, we employ graphical methods to compare and discuss the findings within the generalized uncertainty principle (GUP) and extended uncertainty principle (EUP).

gr-qc↗

arXiv2025

Universal thermodynamic topological classes of static black holes in Conformal Killing Gravity

In this study, we develop universal thermodynamic topological classes for the static black holes in the context of the Conformal Killing Gravity. Our findings indicate that the Conformal Killing Gravity significantly reconstructs the thermodynamic properties of both the smallest inner and the largest outer black hole states. Additionally, it considerably alters the thermodynamic stability of black holes across both high-temperature and low-temperature regimes. This analysis shows that different CKG parameter settings will lead to $W^{0+}$ $(λ>0)$ and $W^{1+}$ $(λ<0)$ categories for the charged AdS black hole, the Reissner-Nordstr$\ddot{o}$m black hole in Conformal Killing Gravity is classified into the $W^{0+}$ and $W^{1+}$ categories. Furthermore, we examine the specific scenario where charge is neglected. The study reveals that within the framework of Conformal Killing Gravity, the Schwarzschild black hole similar to the Schwarzschild-AdS black hole, can be classified into the $W^{1-}$ and $W^{0-}$ categories. This work provides key insights into the fundamental nature of quantum gravity theory.

gr-qc↗

arXiv2025

Black Holes in Proca-Gauss-Bonnet Gravity with Primary Hair: Particle Motion, Shadows, and Grey-Body Factors

We investigate classical and semiclassical signatures of black holes in a recently proposed Proca-Gauss-Bonnet gravity model that admits asymptotically flat solutions with primary hair. Two distinct classes of spherically symmetric metrics arise from different relations between the coupling constants of scalar-tensor and vector-tensor Gauss-Bonnet interactions. For each geometry, we examine the range of parameters permitting horizon formation and analyze the motion of test particles and light rays. We compute characteristic observables including the shadow radius, Lyapunov exponent, innermost stable circular orbit (ISCO) frequency, and binding energy. Additionally, we study scalar and Dirac field perturbations, derive the corresponding effective potentials, and calculate the grey-body factors (GBFs) using both the sixth-order Wentzel-Kramers-Brillouin (WKB) method and their correspondence with quasinormal modes (QNMs). Our results show that the QNM-based approximation of GBFs is accurate for sufficiently large multipole numbers and that deviations from Schwarzschild geometry become pronounced for large values of the Proca hair and Gauss-Bonnet couplings.

gr-qc↗

arXiv2025

Schwarzschild black hole surrounded by a cloud of strings in the background of perfect fluid dark matter

This manuscript investigates a Schwarzschild black hole surrounded by perfect fluid dark matter embedded in a cloud of strings. The effects of its surroundings on thermodynamics, timelike and null geodesics, shadows, and quasinormal modes are analyzed. It is demonstrated that changes in spacetime, induced by the surrounding environment, significantly influence the stability, thermal phases, energy dynamics, particle trajectories, and observable features of the black hole's shadow, as well as the oscillation frequency and decay rate.

gr-qc↗

arXiv2022

Quantum corrections to the quasinormal modes of the Schwarzschild black hole

Based on the minimum measurable momentum concepts associated with the quantum gravity effects acting on the large-scale dynamics of the universe, we study the quantum effect of the EUP on the Hawking evaporation of the black hole. The results show the quantum corrections may shorten the lifetime of the massive black hole. To verify the new EUP on the black hole stability, the scalar field and electromagnetic field are derived and the time evolution of the black hole is analyzed in terms of the time domain integration method, the quantum effect alters the oscillation and decay time of black hole. Furthermore, we use the WKB numerical approximation method to calculate the quasinormal mode frequencies and analyze the influence of the EUP parameter $α$ on the scattering problem. This shows that the EUP significantly increases the area of the total absorption cross-section of the black hole.

gr-qc↗

arXiv2021

Black hole thermodynamics in the presence of a maximal length and minimum measurable in momentum

In this work, incorporating the effect of the minimum measurable in momentum and maximal length, we studied thermodynamics property of Schwarzschild black hole and the Unruh effect. {\color{red} According to this scenario, we see that the black hole temperature cannot be smaller than a certain minimum value of $ T_{\min} $. Moreover, we find that black hole mass cannot be larger than a maximum mass value of $M_{\max }$. Considering these findings first we compute the corrected Hawking temperature versus the mass and examine its characteristic behavior. Then, we derive the black hole's entropy and heat capacity. We find that the black hole is stable when $\frac{M_{\max }}{\sqrt{3}}<M<M_{\max }$. Finally, we examined the modified Unruh effect. We find that the modified Unruh temperature explicitly depends on $α$.

gr-qc↗

arXiv2020

Investigation of Unruh temperature of Black holes by using of EGUP formalism

In this paper, we have used the extended generalized uncertainty principle to investigate the Unruh temperature and thermodynamic properties of a black hole. We started with a brief perusal of the Heisenberg uncertainty principle and continue with some physical and mathematical discussion for obtaining the generalized and the extended generalized uncertainty principle. Then, we obtained the Unruh temperature, mass-temperature, specific heat, and entropy functions of a black hole. We enriched the paper with graphical analysis as well as their comparisons.

gr-qc↗

arXiv2018

An Investigation of the Bound State Solutions of the Klein-Gordon Equation for the Generalized Woods-Saxon Potential in Spin Symmetry and Pseudo-spin Symmetry Limits

Recently, scattering of a Klein-Gordon particle in the presence of mixed scalar-vector generalized symmetric Woods-Saxon potential was investigated for the spin symmetric and the pseudo-spin symmetric limits in one spatial dimension. In this manuscript, the bound state solutions of the Klein-Gordon equation with mixed scalar-vector generalized symmetric Woods-Saxon potential are examined analytically within the framework of spin and pseudo-spin symmetry limits. We prove that the occurrence of bound state energy spectrum exists only in the spin symmetric limit, while in the pseudo-spin symmetric limit, the bound state spectrum does not exist. Besides the theoretical proof, the Newton-Raphson numerical methods are used to calculate the bound state energy spectra of a neutral Kaon particle, confined in a generalized symmetric Woods-Saxon potential, energy well constituted with repulsive or attractive surface interactions, for the spin and pseudo-spin symmetric limits, respectively. Numerical results are consistent with the non-existence of the bound state energy spectrum in the pseudo-spin symmetric limit.

nucl-th↗