Article
Astronomy & Astrophysics
Zeus S. Moreira, Haroldo C. D. Lima Jr, Luis C. B. Crispino, Carlos A. R. Herdeiro
Summary: In this study, we analyze the quasinormal modes (QNMs) of a Schwarzschild black hole with corrections motivated by Loop Quantum Gravity (LQG). The black hole exhibits a global structure of a black bounce, and the QNM frequency orbits in the complex plane are self-intersecting spiraling curves. The overall damping decreases with increasing LQG parameter, and the spectrum of the quantum corrected black hole shows an oscillatory pattern with possible QNMs having vanishing real part.
Article
Astronomy & Astrophysics
Mariano Cadoni, Mauro Oi, Andrea P. Sanna
Summary: By describing the black hole as a statistical ensemble of quantum harmonic oscillators and working in the canonical ensemble, it is shown that in the large-mass black hole limit, the leading contribution to the entropy is the Bekenstein-Hawking term, with a subleading contribution being a logarithmic correction. The number of oscillators is found to scale holographically with the area of the event horizon.
Article
Physics, Particles & Fields
Luis A. H. Mamani, Angel D. D. Masa, Lucas Timotheo Sanches, Vilson T. Zanchin
Summary: In this study, we calculate the quasinormal modes of spin 0, 1/2, 1, 3/2, 2, and 5/2 fields in the asymptotically flat Schwarzschild black hole spacetime using numerical methods. We compare the results with the available literature and test different numerical methods. Additionally, we obtain purely imaginary frequencies for spin 1/2, 3/2, and 5/2 fields, which are consistent with previous analytic results.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Multidisciplinary
M. A. Anacleto, J. A. Campos, F. A. Brito, E. Passos
Summary: This study investigates quantum corrections to the Schwarzschild black hole metric using the generalized uncertainty principle (GUP) and explores its effects on quasinormal modes, shadow, and their relationship in the eikonal limit. The research utilizes the sixth-order Wentzel-Kramers-Brillouin (WKB) approximation to calculate quasinormal frequencies and confirms the results through numerical analysis. Interestingly, the shadow radius is found to be nonzero even at very small mass limits for finite GUP parameter.
Article
Astronomy & Astrophysics
N. Heidari, H. Hassanabadi
Summary: This paper presents a new analytical approach using the Rosen-Morse function to calculate the Quasi Normal Modes (QNMs) of black holes. The proposed method provides a more precise approximation compared to previous methods. The corrected modes based on this research are claimed to be a generalized form of QNMs found by the Posch-Teller function. Numerical results of the new approach are calculated and compared with results obtained by the Mashhoon method and numerical method.
Article
Astronomy & Astrophysics
A. Martinez-Merino, M. Sabido
Summary: In this study, the lowest value of black hole spin is investigated using non-extensive entropies. The results show that the spin depends on the area and non-extensive parameter, with the modification only present for micro black holes.
Article
Astronomy & Astrophysics
Koutarou Kyutoku, Hayato Motohashi, Takahiro Tanaka
Summary: We investigate the scattering of gravitational waves by a Schwarzschild black hole and its perturbed siblings to examine the effect of proposed spectral instability of quasinormal modes on the ringdown signal. Our findings show that the information of dominant ringdown signals, associated with the least damping quasinormal mode of unperturbed Schwarzschild black holes, is imprinted in the phase shift of the transmission amplitude. This behavior is analogous to the resonance of quantum systems being imprinted in the phase shift of the S matrix. The phase shift near the oscillation frequency of the fundamental mode is only perturbatively modified, indicating the stability of the ringdown signal, while the phase shift at low frequencies is significantly modulated due to the late-time excitation of echo signals associated with the destabilized quasinormal-mode spectrum.
Article
Astronomy & Astrophysics
Che-Yu Chen, Hsu -Wen Chiang, Jie-Shiun Tsao
Summary: This study explores the appearance of eikonal correspondence in asymmetric spacetimes and finds explicit eikonal correspondence in deformed Schwarzschild spacetime.
Article
Astronomy & Astrophysics
Jerzy Matyjasek
Summary: This paper aims to construct accurate frequencies of the quasinormal modes of the five-dimensional Schwarzschild-Tangherlini black hole using three major techniques and discusses the limitations of each. The results show that the Hill determinant method and the continued fractions method often yield identical results, while the WKB-Pade method is remarkably accurate in most cases but may have exceptions. The deviations in frequency accuracy for different perturbations are also analyzed.
Article
Physics, Multidisciplinary
Zening Yan, Xiaoji Zhang, Maoyuan Wan, Chen Wu
Summary: In this paper, we investigated the quasinormal modes (QNMs) of a charged non-commutative black hole in scalar, electromagnetic and gravitational fields using three methods. The influence of the non-commutative parameter ? and the charge Q on QNMs in different fields was analyzed. The shadow radius of the black hole was calculated and the valid range of ? and Q was determined based on the constraints from the event horizon telescope. Furthermore, we evaluated the relative deviation (dR(s)) of the shadow radius between non-commutative and commutative spacetimes, revealing that the distinction becomes harder with an increase in the black hole's charge.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Physics, Particles & Fields
Mengjie Wang, Zhou Chen, Qiyuan Pan, Jiliang Jing
Summary: The study generalizes previous research on Maxwell quasinormal modes around Schwarzschild-anti-de-Sitter black holes by introducing a global monopole and applying Robin-type vanishing energy flux boundary conditions. The Maxwell equations are formulated in two formalisms and solved analytically in pure anti-de Sitter spacetimes with a global monopole, revealing two different normal modes due to the monopole parameter. The Maxwell quasinormal spectrum is analyzed by varying angular momentum quantum number l, overtone number N, and the monopole parameter 8 pi eta 2, demonstrating that the global monopole produces a repulsive force.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Multidisciplinary Sciences
J. A. Campos, M. A. Anacleto, F. A. Brito, E. Passos
Summary: This paper investigates the quasinormal modes for a scalar field around a noncommutative Schwarzschild black hole, and verifies the effect of noncommutativity on quasinormal frequencies using two widely used methods. It is found that the shadow radius decreases as the noncommutative parameter increases, and the shadow radius is nonzero even at the zero mass limit for finite noncommutative parameter.
SCIENTIFIC REPORTS
(2022)
Article
Physics, Multidisciplinary
H. Chen, T. Sathiyaraj, H. Hassanabadi, Y. Yang, Z. -W. Long, F. -Q. Tu
Summary: This paper investigates the quasinormal modes of the Schwarzschild black hole under the extended generalized uncertainty principle (EGUP) with the minimal length and momentum. The EGUP-corrected black hole metric function is derived, indicating that quantum effects do not alter the event horizon. The perturbation of the quantum-corrected black hole with scalar and electromagnetic fields is considered, and the effect of quantum correction on the time evolution is analyzed.
INDIAN JOURNAL OF PHYSICS
(2023)
Article
Astronomy & Astrophysics
Shobhit Giri, Hemwati Nandan
Summary: This study investigates the stability of timelike and null circular geodesics in the vicinity of a dual stringy black hole spacetime using Lyapunov exponents. Results show that the coordinate time Lyapunov exponent is independent of magnetic charge parameter for magnetically charged stringy black holes. By establishing a relation between quasinormal modes and parameters related to null circular geodesics, QNMs for massless scalar field perturbations around the stringy black hole spacetime are deduced in the eikonal limit.
GENERAL RELATIVITY AND GRAVITATION
(2021)
Article
Astronomy & Astrophysics
Wei Xiong, Peng Liu, Cheng-Yong Zhang, Chao Niu
Summary: In this study, we investigate the quasinormal modes of charged scalar perturbations in the background of an Einstein-Maxwell-aether black hole using three different methods. We propose a specific treatment for the generalized effective potential and present the complete procedure for transforming the calculation continued fraction method. The results from different methods are consistent, validating the reliability of these methods. Additionally, we explore the allowed region for the second kind aether black hole among the system parameters and demonstrate the existence of quasiresonances of massive perturbations even with a large aether parameter in the Einstein-Maxwell-aether black hole.
Article
Physics, Mathematical
Chevarra Hansraj, Rituparno Goswami, Sunil D. D. Maharaj
Summary: In this paper, we study conformally symmetric generalized Vaidya spacetimes with composite null dust and null string matter distribution using a decomposition method. Our analysis reveals that the geometric variables related to both time-like and preferred space-like congruences are completely determined by the conformal vector and conformal factor. This uniqueness arises from the specific matter distribution of the generalized Vaidya configuration. Additionally, we demonstrate that a proper conformal Killing vector cannot be admitted in the case of pure null dust (or Vaidya) spacetime.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Physics, Multidisciplinary
Noeleen Naidoo, Sunil D. Maharaj, Keshlan S. Govinder
Summary: A model of a radiating star undergoing gravitational collapse is constructed by studying the boundary condition and equation of state. New classes of exact solutions with acceleration, expansion and shear in the presence of the cosmological constant are obtained. The range of the equation of state parameters allows the solution to be interpreted as barotropic matter stars or dark energy stars. The model is physically reasonable and satisfies the energy conditions.
Article
Astronomy & Astrophysics
Byron P. Brassel, Sunil D. Maharaj, Rituparno Goswami
Summary: The junction conditions for a higher dimensional spherically symmetric charged and anisotropic static star in Einstein-Gauss-Bonnet (EGB) gravity with nonvanishing cosmological constant are derived. It is shown that the generalised matching conditions are satisfied across the timelike boundary hypersurface of zero thickness in EGB gravity. The validity of Israel-Darmois conditions is a sufficient condition for the matching. Therefore, a complete stellar model can be generated in EGB gravity. The interior matches to the exterior higher dimensional charged Boulware-Deser spacetime with cosmological constant. The vanishing of barotropic radial pressure at the boundary of the star is also consistent with general relativity.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Physics, Multidisciplinary
Shobhit Giri, Pankaj Sheoran, Hemwati Nandan, Sanjar Shaymatov
Summary: The main objective of this study is to investigate the orbits of spinning test particles around a Schwarzschild black hole under the influence of a quintessence matter field. The dynamics of the spinning test particles are described by the Mathisson-Papapetrou-Dixon equations under the pole-dipole approximation, neglecting the gravitational field and higher multipoles of the particle. The study addresses the classification of effective potentials based on saddle point types, discusses the possibility of chaotic orbits, and explores the innermost stable circular orbits of spinning particles around the black hole.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
Shavani Naicker, Sunil D. Maharaj, Byron P. Brassel
Summary: In this study, we investigated the influence of higher order curvature terms on the static configuration of a charged dust distribution in EGB gravity. We found exact solutions to the governing equations using special functions, series, and polynomials. The results show that the charged dust model behaves well in the center region and can generate dust spheres. The higher order curvature terms have a distinct influence on the dynamics of charged dust and gravitational behavior compared to general relativity.
GENERAL RELATIVITY AND GRAVITATION
(2023)
Article
Physics, Particles & Fields
Shavani Naicker, Sunil D. Maharaj, Byron P. Brassel
Summary: In this paper, the field equations for a charged gravitating perfect fluid in Einstein-Gauss-Bonnet gravity are derived in all spacetime dimensions. The static and spherically symmetric spacetime leads to a charged condition of pressure isotropy, which is a second-order Abel differential equation. It is shown that this equation can be simplified to a first-order, nonlinear canonical differential equation in higher dimensions. The canonical form allows for an exact solution generating algorithm, resulting in implicit solutions by choosing potentials and the electromagnetic field. An exact solution to the canonical equation is found, which corresponds to the neutral model previously discovered. Additionally, three new classes of solutions are obtained by placing constraints on the canonical differential equation, without specifying gravitational potentials and electromagnetic field. When the canonical form is not applicable, other classes of exact solutions are presented using elementary and special functions (the Heun confluent functions).
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
C. Hansraj, R. Goswami, S. D. Maharaj
Summary: In this paper, the Kerr spacetime is analyzed using a semi-tetrad decomposition. The 1+1+2 covariant method is applied to describe the geometry of the Kerr spacetime outside the horizon. A comparison is made between observers in the Killing frame and the ZAMO frame, resulting in different geometrical quantities and equations. This novel approach provides new insights into the Kerr spacetime geometry in a transparent manner.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Sunil D. Maharaj, Noeleen Naidoo, Gareth Amery, Keshlan S. Govinder
Summary: The Karmarkar embedding condition in different spherically symmetrical metrics is studied using Lie symmetries. The study extends recent results by investigating the Lie symmetries for conformally flat and shear-free metrics. Additionally, the Lie symmetries for geodesic metrics and general spherical spacetimes are obtained for the first time. The study also demonstrates that the Karmarkar condition can be used to produce an embeddable relativistic radiating star with a barotropic equation of state via Lie symmetries.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Geosciences, Multidisciplinary
Chhavi P. Pandey, Vineet Ahuja, Lokesh K. Joshi, Hemwati Nandan
Summary: This research focuses on the statistical modelling of monthly maximum precipitation and temperature in Uttarakhand, India, over the last century using extreme value theory. The goal is to provide statistical information on extreme temperatures and precipitation for disaster management organizations and government policymakers to determine appropriate risk mitigation measures.
JOURNAL OF EARTH SYSTEM SCIENCE
(2023)
Article
Physics, Particles & Fields
Noeleen Naidoo, Sunil D. Maharaj, Keshlan S. Govinder
Summary: The objective of this study is to investigate spherically symmetric radiating stars undergoing gravitational collapse, in higher dimensional general relativity, inclusive of acceleration, expansion, shear, an electromagnetic field and a cosmological constant. Two approaches are studied to obtain exact solutions to the boundary condition with/without a linear equation state. Transformations that map the boundary condition into a new Riccati equation are investigated to obtain new exact models. The importance of these transformations in reducing the order of the boundary condition and obtaining new solutions is shown.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Multidisciplinary
Alberto K. Mathias, Jefta M. Sunzu, Sunil D. Maharaj, Jason M. Mkenyeleye
Summary: Exact solutions for charged relativistic anisotropic stars are generated using the Karmarkar condition with Einstein-Maxwell field equations and a linear equation of state. The Bannerji and Durgapal transformation is employed to transform the nonlinear differential equations and field equations. The embedding approach provides a relationship between gravitational potentials, helping to solve and integrate the field equations. The detailed physical analysis shows that the model satisfies necessary conditions such as stability, equilibrium, energy conditions, and the mass-radius relationship.
PRAMANA-JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
J. W. Jape, S. D. Maharaj, J. M. Sunzu, J. M. Mkenyeleye
Summary: We generate charged anisotropic exact models with a conformal Killing vector for static spacetime, which satisfies various physical requirements and regains some known solutions.
INDIAN JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
J. W. Jape, J. M. Sunzu, S. D. Maharaj, J. M. Mkenyeleye
Summary: Exact solutions of charged anisotropic fluid spheres with a linear equation of state are generated by incorporating conformal symmetry and an equation of state. These solutions satisfy several important physical conditions, including smooth matching, compatibility with observations, and stability requirement.
INDIAN JOURNAL OF PHYSICS
(2023)
Article
Physics, Particles & Fields
Byron P. Brassel, Sunil D. Maharaj, Rituparno Goswami
Summary: We generalize the collapse of a spherically symmetric radiation shell with an electromagnetic field in five-dimensional Einstein-Gauss-Bonnet gravity. The presence of charge significantly affects the collapse dynamics, leading to the emergence of a branch singularity separating the physical spacetime from the complex region. We show that this difference in singularity formation is unique to five dimensions, as in higher dimensions the charged collapse terminates with the same branch singularity as in five dimensions. The comparison with charged radiation collapse in general relativity is also provided.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Particles & Fields
Shobhit Giri, Hemwati Nandan, Lokesh Kumar Joshi, Sunil D. Maharaj
Summary: This study examines the stability of circular orbits in a traversable wormhole spacetime and employs the Lyapunov stability approach to determine the motion characteristics of non-spinning test particles in this spacetime.
EUROPEAN PHYSICAL JOURNAL C
(2022)
