Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2002.10496

Black Hole Superradiance in f(R) Gravities

Mohsen Khodadi·Alireza Talebian·Hassan Firouzjahi
View original source ↗Read source document ↗Export metadata ↓

Abstract

We study the superradiance amplification factor (SAF) for a charged massive scalar wave scattering off small and slowly rotating Kerr-Newman black holes in $f(R)$ gravity immersed in asymptotically flat and de-Sitter spacetimes. We employ the \emph{``analytical asymptotic matching''} approximation technique which is valid in low frequency regime where the Compton wavelength of the propagating particle is much larger than the size of the black hole. The $f(R)$-Kerr-Newman family solution induces an extra distinguishable effect on the contribution of the black hole's electric charge to the metric and that in turn affects the SAFs and their frequency ranges. While our analysis are general, we present the numerical results for the Starobinsky and Hu-Sawicki $f(R)$ models of gravity as our working examples. In the case of asymptotically flat spacetime, the SAFs predicted in Starobinsky $f(R)$ model are not distinguishable from those of GR while for Hu-Sawicki model the SAFs can be weaker or stronger than those of GR within the frequency parameters space. In the case of asymptotically de-Sitter spacetime, the superradiance scattering may not either occur in Starobinsky model or has a weaker chance compared to GR while in Hu-Sawicki model the results of SAFs and their frequency regimes are different from the standard ones.

Explore related subjects

gr-qcastro-ph.HEhep-th

Keep this discovery

BibTeXRIS

Mohsen Khodadi, Alireza Talebian, Hassan Firouzjahi. 2020-02-24. Black Hole Superradiance in f(R) Gravities. https://arxiv.org/abs/2002.10496

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Electrovacuum Black Hole Uniqueness

We prove the black hole uniqueness conjecture in the axially symmetric, stationary, electrovacuum setting, subject to the refined asymptotic analysis of the associated singular harmonic maps, which includes an analyticity hypothesis at the axes. More precisely, it is shown that any asymptotically flat solution of the Einstein--Maxwell equations in this class, with more than one black hole horizon component is either: Majumdar--Papapetrou, up to a duality rotation, in which case all logarithmic angle defects vanish, or every finite axis rod logarithmic angle defect is strictly negative and hence every interaction force is strictly attractive. The proof extends the singular harmonic map method used for vacuum Kerr uniqueness in [18].

gr-qc↗
arXiv2026

Constraining Modified Mass-to-Horizon Cosmology Through Primordial Inflationary Observables

We investigate slow-roll inflation in a modified cosmological framework inspired by a generalized mass-to-horizon relation (MHR), $M=\gamma {c^2 L^n}/{G}$, where $n$ is a real parameter and $\gamma$ a dimensional constant. Using Padmanabhan's emergence paradigm, we derive the modified Friedmann equations for a flat FRW universe and analyze the dynamics of a canonical scalar field (inflaton) under the slow-roll approximation. We study the resulting inflationary phenomenology for power-law and Starobinsky potentials. For power-law potentials, the MHR modification fails to reconcile these models with current CMB constraints on $r$ and $n_s$. In contrast, Starobinsky inflation exhibits significant sensitivity to deviations from $n=1$. A perturbative analysis ($n=1+\Delta$) yields corrections to inflationary observables. We observe that the scalar power-spectrum normalization, under a fixed-Starobinsky prescription, imposes the stringent constraint $0.960 \lesssim n \lesssim 1.040$ for $N=60$ efolds. This is considerably tighter than spectral-index bounds. Our results establish inflation, particularly Starobinsky-like models, as a sensitive probe of generalized horizon thermodynamics and departures from standard MHR scaling.

gr-qc↗
arXiv2026

Improving the Sensitivity of Gravitational Wave Detection with Weighted Conformal Prediction

In the last decade, kilometre-scale interferometric gravitational-wave detectors have observed hundreds of compact binary mergers, the majority of which are binary black holes. However, the data are noise-dominated, and multiple independent search algorithms (pipelines) are used to enhance sensitivity and improve robustness. Rather than the standard approach of selecting the most significant pipeline output, we combine the outputs from all pipelines using a conformal prediction-based framework to provide statistically rigorous confidence estimates for candidate events. While combining pipelines improves sensitivity and ranking robustness, it requires a principled statistical framework that remains valid as data properties evolve across observing runs. A key challenge is distribution shifts between simulated datasets used for training and calibration and the real, unlabelled, observations used for testing, which can invalidate coverage guarantees and bias confidence estimates. In this work, we address this challenge by incorporating likelihood-ratio reweighting into our conformal prediction framework to account for covariate shift. Using mock datasets containing simulated signals, we demonstrate that weighted conformal prediction restores well-calibrated coverage under covariate shift and increases the confidence of events near the detection threshold, recovering true signals that would otherwise be missed.

gr-qc↗