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14 pages, 3234 KB

Open AccessArticle

Scalar Greybody Radiation of “NRIGP” Black Hole

by Sara Kanzi

Symmetry 2025, 17(1), 42; https://doi.org/10.3390/sym17010042 - 29 Dec 2024

Cited by 1 | Viewed by 770

The present paper investigates the greybody radiation of a general metric including the significant black hole parameters. The fraction of Hawking radiation (HR) that succeeds in achieving infinity is known as “greybody radiation” or transmission probability. In this study, the focus is on [...] Read more.

The present paper investigates the greybody radiation of a general metric including the significant black hole parameters. The fraction of Hawking radiation (HR) that succeeds in achieving infinity is known as “greybody radiation” or transmission probability. In this study, the focus is on the black hole parameters by which greybody radiation could be affected, such as electric and magnetic charges “e” and “g”, respectively, cosmological constant “

Λ

”, and Taub-Nut “l”. In this regard, we use the nonrotating form of the improved Griffiths–Podolsk (NRIGP) metric which contains the factors “

Λ, l, e, g

”, all in a single metric. This study allows us to observe the behavior of the scalar perturbation and greybody radiation of each indicated parameter in the presence of the other variables. The spacetime around the black hole behaves as a barrier for particles, and the greybody factor strongly depends on the black hole potential barrier. Therefore, we first studied the scalar perturbation and evaluated the actions of the effective potential by the regarded parameters. The depicted figures for variables such as magnetic charge “g” confirm the consistency between the effective potential and the greybody factor. In this area of study, symmetry plays an essential but hidden role. In the current study, we also consider that all the particles around a black hole have the same symmetry. Full article

(This article belongs to the Section Physics)

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21 pages, 3926 KB

Open AccessArticle

Probing the Lorentz Invariance Violation via Gravitational Lensing and Analytical Eigenmodes of Perturbed Slowly Rotating Bumblebee Black Holes

by Mert Mangut, Huriye Gürsel, Sara Kanzi and İzzet Sakallı

Universe 2023, 9(5), 225; https://doi.org/10.3390/universe9050225 - 12 May 2023

Cited by 29 | Viewed by 2016

Abstract

The ability of bumblebee gravity models to explain dark energy, which is the phenomenon responsible for the universe’s observed accelerated expansion, is one of their most significant applications. An effect that causes faster expansion can be linked to how much the Lorentz symmetry [...] Read more.

The ability of bumblebee gravity models to explain dark energy, which is the phenomenon responsible for the universe’s observed accelerated expansion, is one of their most significant applications. An effect that causes faster expansion can be linked to how much the Lorentz symmetry of our universe is violated. Moreover, since we do not know what generates dark energy, the bumblebee gravity theory seems highly plausible. By utilizing the physical changes happening around a rotating bumblebee black hole (RBBH), we aim to obtain more specific details about the bumblebee black hole’s spacetime and our universe. However, as researched in the literature, slow-spinning RBBH (SRBBH) spacetime, which has a higher accuracy, will be considered instead of general RBBH. To this end, we first employ the Rindler–Ishak method (RIM), which enables us to study how light is bent in the vicinity of a gravitational lens. We evaluate the deflection angle of null geodesics in the equatorial plane of the SRBBH spacetime. Then, we use astrophysical data to see the effect of the Lorentz symmetry breaking (LSB) parameter on the bending angle of light for numerous astrophysical stars and black holes. We also acquire the analytical greybody factors (GFs) and quasinormal modes (QNMs) of the SRBBH. Finally, we visualize and discuss the results obtained in the conclusion section. Full article

(This article belongs to the Special Issue Advances in Gravitational Lensing and Gravitational Waves Research)

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20 pages, 797 KB

Open AccessArticle

Superradiant (In)stability, Greybody Radiation, and Quasinormal Modes of Rotating Black Holes in Non-Linear Maxwell f(R) Gravity

by Sara Kanzi, İzzet Sakallı and Behnam Pourhassan

Symmetry 2023, 15(4), 873; https://doi.org/10.3390/sym15040873 - 6 Apr 2023

Cited by 6 | Viewed by 1951

Abstract

This work is dedicated to the investigation of the superradiant stability of a rotating black hole derived from the nonlinear Maxwell theory of gravity,

f (R)

. The evaluation of stability and instability in this study will be based on the [...] Read more.

This work is dedicated to the investigation of the superradiant stability of a rotating black hole derived from the nonlinear Maxwell theory of gravity,

f (R)

. The evaluation of stability and instability in this study will be based on the absence and presence of the magnetic field, respectively, when the magnetic field constant is

c_{4} = 0

and

c_{4} \neq 0

. For the black hole under discussion, analyses of the greybody factors (GFs) and quasi-normal modes (QNMs) are also carried out. To this end, we first consider the Klein–Gordon equation for the scalar waves propagating in the black hole’s geometry. The resulting radial equation is then reduced to a one-dimensional Schrödinger-like wave equation with effective potential energy. The effects of the nonlinear Maxwell

f (R)

gravity theory parameters (q, c, and

c_{4}

) on the effective potential, GFs, and QNMs are examined. The results demonstrate that, although the parameters q, c, and

c_{4}

all influence the effective potential, they do not affect the GFs and QNMs. All results are presented and summarized using appropriate graphics and tables. Full article

(This article belongs to the Section Physics)

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16 pages, 512 KB

Open AccessArticle

Fermionic Greybody Factors in Schwarzschild Acoustic Black Holes

by Sara Kanzi and İzzet Sakallı

Universe 2023, 9(2), 108; https://doi.org/10.3390/universe9020108 - 19 Feb 2023

Cited by 6 | Viewed by 1862

Abstract

In Schwarzschild acoustic black hole (SABH) spacetime, we investigate the wave dynamics for the fermions. To this end, we first take into account the Dirac equation in the SABH by employing a null tetrad in the Newman–Penrose (NP) formalism. Then, we consider the [...] Read more.

In Schwarzschild acoustic black hole (SABH) spacetime, we investigate the wave dynamics for the fermions. To this end, we first take into account the Dirac equation in the SABH by employing a null tetrad in the Newman–Penrose (NP) formalism. Then, we consider the Dirac and Rarita–Schwinger equations, respectively. The field equations are reduced to sets of radial and angular equations. By using the analytical solution of the angular equation set, we decouple the radial wave equations and obtain the one-dimensional Schrödinger-like wave equations with their effective potentials. The obtained effective potentials are graphically depicted and analyzed. Finally, we investigate the fermionic greybody factors (GFs) radiated by the SABH spacetime. A thorough investigation is conducted into how the acoustic tuning parameter affects the GFs of the SABH spacetime. Both the semi-analytic WKB method and bounds for the GFs are used to produce the results, which are shown graphically and discussed. Full article

(This article belongs to the Special Issue Quantum Field Theory in Curved Spacetime and Its Implications for Cosmology, Blackholes and Quantum Gravity)

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18 pages, 589 KB

Open AccessArticle

Weak Deflection Angle, Hawking Radiation and Greybody Bound of Reissner–Nordström Black Hole Corrected by Bounce Parameter

by Wajiha Javed, Mehak Atique, Reggie C. Pantig and Ali Övgün

Symmetry 2023, 15(1), 148; https://doi.org/10.3390/sym15010148 - 4 Jan 2023

Cited by 24 | Viewed by 2478

Abstract

In this study, we probe the weak lensing by a Reissner–Nordström black hole corrected by bounce parameter in plasma and dark matter mediums. For this, the optical geometry and the Gibbons–Werner approach are utilized to obtain the bending angle in the weak field [...] Read more.

In this study, we probe the weak lensing by a Reissner–Nordström black hole corrected by bounce parameter in plasma and dark matter mediums. For this, the optical geometry and the Gibbons–Werner approach are utilized to obtain the bending angle in the weak field limitations. We examine that the impact of these mediums increases the black hole’s bending angle. In addition, we graphically study the deflection angle of light with respect to the impact parameter and examine that the bounce parameter directly affects the angle. Further, we compute the Hawking radiation via a topological method involving two invariants and verify our obtained result with the standard method of calculating the Hawking temperature. In addition, we compute the greybody factor’s bound of the black hole. Moreover, we analyze the bound graphically and observe that the bound shows convergent behavior. We also study that our attained results reduce the results of the Reissner–Nordström and Schwarzschild black holes by reducing the parameters. Finally, we probe how the bounce parameter affected the shadow radius and compared it to the shadow produced if the black hole is immersed in plasma. It is revealed that the rate at which the shadow radius changes with respect to r easily tends to zero under the effect of the bounce parameter, while the plasma merely increases the shadow radius. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

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13 pages, 778 KB

Open AccessArticle

Weak Deflection Angle and Greybody Bound of Magnetized Regular Black Hole

by Wajiha Javed, Sibgha Riaz and Ali Övgün

Universe 2022, 8(5), 262; https://doi.org/10.3390/universe8050262 - 25 Apr 2022

Cited by 17 | Viewed by 2391

Abstract

In this paper, we examine the weak deflection angle and greybody bound for a magnetized regular black hole. For this purpose, we apply the Gauss–Bonnet theorem on the black hole and obtain the deflection angle in plasma and non-plasma mediums. Moreover, we investigate [...] Read more.

In this paper, we examine the weak deflection angle and greybody bound for a magnetized regular black hole. For this purpose, we apply the Gauss–Bonnet theorem on the black hole and obtain the deflection angle in plasma and non-plasma mediums. Moreover, we investigate graphically the effect of impact parameter on the deflection angle for regular black hole in both mediums. We examine that the deflection angle goes to infinity when the impact parameter approaches zero. We also observe that the deflection angle shows negative behaviour at

q = 0.6

and

q = 2.09

, but at

0.6 < q < 2.09

, the angle shows positive behaviour. Furthermore, we study the rigorous bound phenomenon of the greybody factor in the background for a magnetized regular black hole. Later, we analyse the graphical behaviour of greybody bound with respect to different values of

ω

and observe that, at small values of

ω

, the bound increases, but for large values, the bound decreases. After that, we examine that, when we put

G = 1

,

l = 0

and

q = 0

, all results for the magnetized regular black hole solution reduce into results of the Schwarzschild black hole solution. Full article

(This article belongs to the Special Issue Dark Matter and Dark Energy: Particle Physics, Cosmology, and Experimental Searches)

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25 pages, 3088 KB

Open AccessArticle

Scattering on Quasi-Spherical Black-Holes: Features and Beyond

by Adam M. Arslanaliev and Alexei J. Nurmagambetov

Physics 2021, 3(1), 17-41; https://doi.org/10.3390/physics3010004 - 28 Jan 2021

Cited by 1 | Viewed by 3692

Abstract

Recent developments in the gravitational waves interferometry require more pertinent theoretical models of gravitational waves generation and propagation. Untouched possible mechanisms of spin-2 spacetime perturbations production, we will consider their subsequent scattering on other black holes (BHs). Specifically, we consider a generalization of [...] Read more.

Recent developments in the gravitational waves interferometry require more pertinent theoretical models of gravitational waves generation and propagation. Untouched possible mechanisms of spin-2 spacetime perturbations production, we will consider their subsequent scattering on other black holes (BHs). Specifically, we consider a generalization of the Regge-Wheeler-Zerilli equations for the case of distorted BHs (BHs surrounded with matter) in Minkowski and Anti-de Sitter spacetimes, the metric potential of which obeys the Liouville equation. We establish significant differences in scattering characteristics of waves of different spins and angular momenta, including the gravitational waves, caused by losing the spherical symmetry of their propagation background. In particular, we demonstrate the strong impact of the background geometry deformation on the grey-body factors, hence on the absorption cross-sections of scattering waves, and explore the issue of stability of the background geometry upon changing the deformation degree parameters. Full article

(This article belongs to the Special Issue Beyond the Standard Models of Physics and Cosmology)

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20 pages, 997 KB

Open AccessFeature PaperArticle

Greybody Factors for Schwarzschild Black Holes: Path-Ordered Exponentials and Product Integrals

by Finnian Gray and Matt Visser

Universe 2018, 4(9), 93; https://doi.org/10.3390/universe4090093 - 3 Sep 2018

Cited by 32 | Viewed by 4399

Abstract

In earlier work concerning the sparsity of the Hawking flux, we found it necessary to re-examine what is known regarding the greybody factors of black holes, with a view to extending and expanding on some old results from the 1970s. Focusing specifically on [...] Read more.

In earlier work concerning the sparsity of the Hawking flux, we found it necessary to re-examine what is known regarding the greybody factors of black holes, with a view to extending and expanding on some old results from the 1970s. Focusing specifically on Schwarzschild black holes, we have re-calculated and re-assessed the greybody factors using a path-ordered-exponential approach, a technique which has the virtue of providing a pedagogically useful semi-explicit formula for the relevant Bogoliubov coefficients. These path-ordered-exponentials, being based on a variant of the “transfer matrix” formalism, are closely related to so-called “product integrals”, leading to quite straightforward and direct numerical evaluation, while side-stepping any need for numerically solving the relevant ordinary differential equations. Furthermore, while considerable analytic information is already available regarding both the high-frequency and low-frequency asymptotics of these greybody factors, numerical approaches seem better adapted to finding suitable “global models” for these greybody factors in the intermediate frequency regime, where most of the Hawking flux is actually concentrated. Working in a more general context, these path-ordered-exponential techniques are also likely to be of interest for generic barrier-penetration problems. Full article

(This article belongs to the Collection Open Questions in Black Hole Physics)

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