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Gravitational radiation from an axion cloud around a black hole: Superradiant phase

7 Pith papers cite this work. Polarity classification is still indexing.

7 Pith papers citing it
abstract

Motivated by possible existence of string axions with ultralight masses, we study gravitational radiation from an axion cloud around a rotating black hole (BH). The axion cloud extracts the rotation energy of the BH by superradiant instability, while it loses energy through the emission of gravitational waves (GWs). In this paper, GWs are treated as perturbations on a fixed background spacetime to derive the energy emission rate. We give an analytic approximate formula for the case where axion's Compton wavelength is much larger than the BH radius, and then, present numerical results without approximation. The energy loss rate of the axion cloud through the GW emission turns out to be smaller than the energy gain rate of the axion cloud by superradiant instability until nonlinear self-interactions of axions become important. In particular, an axion bosenova must happen at the last stage of superradiant instability.

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background 3 method 1

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gr-qc 5 hep-ph 2

representative citing papers

Gravitational Atoms from Topological Stars

gr-qc · 2025-11-13 · unverdicted · novelty 5.0

Bound states of a massive scalar field around topological stars form strictly normal modes, producing a hydrogen-like spectrum when the Compton wavelength exceeds the star size and localized states otherwise.

High-frequency gravitational wave transients from superradiance

gr-qc · 2026-04-01 · unverdicted · novelty 5.0

Ultralight boson clouds around primordial black holes emit high-frequency gravitational wave transients via superradiance and binary-driven transitions, but the signals fall below current detector sensitivity at plausible distances.

Axions as Dark Matter, Dark Energy, and Dark Radiation

hep-ph · 2025-09-21 · unverdicted · novelty 2.0

A mini-review of axion phenomenology showing how light bosons can account for dark matter, drive cosmic acceleration, or contribute to relativistic backgrounds in the early and late Universe.

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