Quasinormal Modes of Slowly Rotating Black Holes in Hernquist Halos: Redshift and Angular Momentum
Abstract
We investigate axial quasinormal modes of black holes embedded in Hernquist halos, using an established analytic static geometry with an inner vacuum cavity extending to 4MBH and solving for frame dragging to first order in rotation. We compute the fundamental and first overtone branches for mass ratios Ξ΅β‘ MBH/Mhalo of $0.1$ and $0.01$, and halo compactness πβ‘ Mhalo/a0 in the range 10β4β€πβ€0.3. The cavity geometry gives a local Kerr estimate in which redshift rescales the vacuum frequencies, horizon angular momentum sets the rotational splitting, and uniform frame dragging adds a real frequency shift. At zero spin, the cavity redshift reproduces the complex β=2 frequencies with relative residuals below 0.04% for the fundamental and 0.31% for the first overtone. Its leading weak compactness behavior, 1βπ, explains the weak mass ratio dependence in dilute halos; at larger compactness, the exact redshift accounts for most of the separation between the two mass ratio sequences. At fixed total angular momentum, halos with vanishing local angular momentum and those with vanishing coordinate angular velocity exhibit opposite compactness trends in the real spin coefficient. At π=0.3, their real fundamental mode spin coefficients differ by approximately 38% and 54% for the two mass ratios. Fixing the horizon angular momentum reduces these differences below 1% for both overtones, showing that angular momentum partition accounts for most of the configuration dependence.
Related
- Intrinsic Angular Momentum Contribution to the Sagnac Response of a Rotating Helical Optical Fiber
- Quasinormal modes of rotating black holes with ultralight scalar fields
- Quasinormal Modes of a Rotating HoΕava Black Hole: Two Perturbative Approaches to Nonseparability
- Signatures of charged rotating regular black holes: quasinormal modes, grey-body factors and shadows
- Optical Angular Momentum Oscillation in Effective Magnetic Field Modulated by Polarization Helicity
BibTeX
@misc{feng2026quasinormal,
title = {{Quasinormal Modes of Slowly Rotating Black Holes in Hernquist Halos: Redshift and Angular Momentum}},
author = {Xing-Hui Feng and Bo Wang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.39548},
eprint = {2610.39548},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.39548},
}
RIS
TY - UNPB
TI - Quasinormal Modes of Slowly Rotating Black Holes in Hernquist Halos: Redshift and Angular Momentum
AU - Xing-Hui Feng
AU - Bo Wang
PY - 2026
DA - 2026/10/29
PB - arXiv
DO - 10.48550/arxiv.2610.39548
UR - https://arxiv.org/abs/2610.39548
AB - We investigate axial quasinormal modes of black holes embedded in Hernquist halos, using an established analytic static geometry with an inner vacuum cavity extending to 4M_BH and solving for frame dragging to first order in rotation. We compute the fundamental and first overtone branches for mass ratios Ξ΅β‘ M_BH/M_halo of $0.1$ and $0.01$, and halo compactness πβ‘ M_halo/a_0 in the range 10^β4β€πβ€0.3. The cavity geometry gives a local Kerr estimate in which redshift rescales the vacuum frequencies, horizon angular momentum sets the rotational splitting, and uniform frame dragging adds a real frequency shift. At zero spin, the cavity redshift reproduces the complex β=2 frequencies with relative residuals below 0.04% for the fundamental and 0.31% for the first overtone. Its leading weak compactness behavior, 1βπ, explains the weak mass ratio dependence in dilute halos; at larger compactness, the exact redshift accounts for most of the separation between the two mass ratio sequences. At fixed total angular momentum, halos with vanishing local angular momentum and those with vanishing coordinate angular velocity exhibit opposite compactness trends in the real spin coefficient. At π=0.3, their real fundamental mode spin coefficients differ by approximately 38% and 54% for the two mass ratios. Fixing the horizon angular momentum reduces these differences below 1% for both overtones, showing that angular momentum partition accounts for most of the configuration dependence.
ER -