Axial Mode Stability and Quasinormal Modes of Charged Kiselev Black Holes in Rastall Gravity
Year: 2026
Type: preprint
Abstract: We investigate axial gravitoelectromagnetic perturbations of charged black holes surrounded by dust-like Kiselev-type anisotropic matter in Rastall gravity. We derive the axial matter compatibility condition and construct a compatible response by holding the covariant anisotropy-direction vector unperturbed. The resulting gravitational and electromagnetic perturbations obey two coupled Schrodinger-type master equations. An r-independent algebraic decoupling exists in the Reissner-Nordstrom and general-relativistic dust-like limits; additional radial structure obstructs it in generic charged Rastall backgrounds with nonzero surrounding matter. We prove axial mode stability under the adopted closure for every nonextremal background satisfying the stated exterior conditions, covering all physical axial multipoles. A matrix S-deformation excludes exponentially growing coupled modes for l >= 2, while the physical electromagnetic dipole has a positive effective potential. A Chebyshev pseudospectral calculation, validated against the Reissner-Nordstrom spectrum and spectral convergence, determines the fundamental frequencies. In the parameter ranges examined, increasing the Rastall coupling lowers both the oscillation frequency and the damping rate in the small-coupling region; in the large-coupling region, the oscillation frequency rises while the damping rate varies nonmonotonically. A larger charge generally raises the oscillation frequency, whereas stronger surrounding-matter contributions produce longer-lived modes.
Source: arXiv (Cornell University)
Authors: Wang, Yan, Gu, Yun-tao, Guo, Wen-Di
Institution: Lanzhou University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214121506