We investigate the absorption cross sections of electromagnetic perturbations propagating on a four-dimensional brane in the background of higher-dimensional regular black holes arising in quasi-topological gravity. Employing a WKB-based approach for the computation of greybody factors, we analyze the impact of higher-curvature corrections and spacetime dimensionality on the scattering properties of the system. We show that regularity effects lead to systematic deviations from the singular Tangherlini solution, manifested in shifts of the absorption spectrum and modifications of the effective photon sphere radius. Increasing the number of spacetime dimensions suppresses these deviations, driving the system toward the classical limit and reducing the number of multipoles required for convergence. In the high-frequency regime, the absorption cross section approaches the geometric-optics limit, while at low frequencies it is strongly suppressed due to diminished transmission probabilities. Our results demonstrate that the interplay between regularity and higher-curvature effects leaves distinct imprints on the absorption characteristics, providing a sensitive probe of the underlying gravitational theory.
A case of non-minimal couplings between gravity and electromagnetic fields is presented. The field equations are worked out in the language of exterior differential forms. An exact charge screening class of solutions is given with a specific discussion on the polarisation and magnetisation of spacetime. The consequences of non-minimal couplings to gravity are examined.
Generating Electromagnetic Waves from Gravity Waves in Cosmology
在Friedmann-Lemaitre-Robertson-Walker（FLRW）背景上的测试电磁波的例子是从描述在各向同性宇宙中传播的引力波的FLRW时空的显式扰动构造的。产生测试电磁波的一种可能的物理机制被证明是引力波与测试磁场的耦合，证实了Marklund、Dunsby和Brodin的观察结果[Phys.Rev. D 62，101501（R）（2000）]。
Electromagnetic Quasinormal modes of Dyonic AdS black holes with quasi-topological electromagnetism in a Horndeski gravity theory mimicking EGB gravity at $D \rightarrow 4$
In this paper, we investigate complexity of anisotropic cylindrical object under the influence of electromagnetic field in $f(G,T)$ theory, where $G$ and $T$ indicate the Gauss-Bonnet term and trace of the stress-energy tensor, respectively. For this purpose, we calculate the modified field equations, non-conservation equation and mass distributions that assist in comprehending the structure of astrophysical objects. The Riemann tensor is divided into different structure scalars, among which one is called the complexity factor. This factor is used to measure complexity of the system due to the…
We find the low lying quasinormal mode frequencies of the recently proposed novel four dimensional Gauss-Bonnet de Sitter black holes for scalar, electromagnetic and Dirac field perturbations using the third order WKB approximation as well as Padé approximation, as an improvement over WKB. We figure out the effect of the Gauss-Bonnet coupling $α$ and the cosmological constant $Λ$ on the real and imaginary parts of the QNM frequencies. We also study the greybody factors and eikonal limits in the above background for all three different types of perturbations.
Dissipative Spherical Collapse of Charged Anisotropic Fluid in f(R) Gravity
本文研究了一个可行的模型f（R）= R + αR^n与电磁场的联合作用对引力坍缩不稳定性范围的影响。我们假设带电各向异性流体通过热流耗散能量，讨论了局部各向异性背景可以包含天体上的电磁场、密度不均匀性、剪切和相变。动力学方程有助于研究自引力天体的演化，并得出绝热指数依赖于电磁背景、天体质量和半径的结论。
In the framework of Higgs inflation, we consider the electromagnetic field nonminimally coupled to gravity via the parity-preserving $\propto RF^{2}$ and parity-violating $\propto RF\tilde{F}$ terms. Using the perturbation theory to the leading order in these couplings, we study the generation of the electromagnetic field during the inflation stage. We derive the effective kinetic and axial coupling functions arising in the Einstein frame in the usual metric as well as Palatini formulations of gravity. For both formulations, we determine the power spectrum, energy density, and helicality of th…
Spontaneous scalarization of regular Hayward black holes in Einstein-nonlinear electromagnetic-scalar gravity
College of Physics and Communication Electronics, Jiangxi Normal University（江西师范大学物理与通信电子学院）；College of Science, Hunan Institute of Technology（湖南科技学院理学院）
Time and Matter in the Interaction between Gravity and Quantum Fluids: Are there Macroscopic Quantum Transducers between Gravitational and Electromagnetic waves?
