Future microhertz detections combined with nanohertz pulsar terms can serve as gravity echoes to measure supermassive black hole binary inspiral rates from hundreds to thousands of years in the past.
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Superradiance -- the 2020 Edition
Canonical reference. 95% of citing Pith papers cite this work as background.
abstract
Superradiance is a radiation enhancement process that involves dissipative systems. With a 60 year-old history, superradiance has played a prominent role in optics, quantum mechanics and especially in relativity and astrophysics. In General Relativity, black-hole superradiance is permitted by the ergoregion, that allows for energy, charge and angular momentum extraction from the vacuum, even at the classical level. Stability of the spacetime is enforced by the event horizon, where negative energy-states are dumped. Black-hole superradiance is intimately connected to the black-hole area theorem, Penrose process, tidal forces, and even Hawking radiation, which can be interpreted as a quantum version of black-hole superradiance. Various mechanisms (as diverse as massive fields, magnetic fields, anti-de Sitter boundaries, nonlinear interactions, etc...) can confine the amplified radiation and give rise to strong instabilities. These "black-hole bombs" have applications in searches of dark matter and of physics beyond the Standard Model, are associated to the threshold of formation of new black hole solutions that evade the no-hair theorems, can be studied in the laboratory by devising analog models of gravity, and might even provide a holographic description of spontaneous symmetry breaking and superfluidity through the gauge-gravity duality. This work is meant to provide a unified picture of this multifaceted subject. We focus on the recent developments in the field, and work out a number of novel examples and applications, ranging from fundamental physics to astrophysics.
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representative citing papers
Using LIGO O3 continuous-wave search data, the authors place the first constraints on ellipticities of self-interacting fermionic dark matter admixed neutron stars and exclude regions of the DM parameter space for masses in [0.1,10] GeV.
An external dynamical environment forms a resonant cavity with a black hole in dCS gravity that triggers Mathieu instability in the scalar sector, producing cascading amplification of gravitational waves via a delayed secondary burst.
Exact transparent radiation boundary conditions and near-to-far field teleportation kernels are derived for the Bardeen-Press equation, approximated via exponential sums with error bounds, and shown to eliminate late-time artifacts in time-domain solvers.
GreyRing model based on greybody factors reproduces numerical relativity ringdown signals with mismatches of order 10^{-6} and enables a new post-merger consistency test of general relativity applied to GW250114.
ABG-dS black holes show charged superradiant instability exclusively for the spherically symmetric ℓ=0 mode, with growth rates that peak at intermediate Λ and q and rise with Q, differing from RN-dS due to nonlinear electrodynamics.
Acceleration radiation for massive vector fields near black hole horizons has a universal thermal detailed-balance factor from the Rindler transformation, with mass thresholds and polarization-dependent spectra, yielding an entropy flux relation identical in form to the scalar HBAR case.
Black hole superradiance constrains the coupling strength in interacting dark energy-dark matter models through modifications to the effective mass of ultralight bosons in two scenarios.
Tailored temporal modulation of incoming signals enables complete absorption by black holes via excitation of complex-plane resonances, storing energy for later release through virtual absorption modes.
Derives a cavity thermal product formula relating bouncing geodesic singularities in the retarded Green's function to the quasinormal mode spectrum for Schwarzschild and Schwarzschild-de Sitter black holes inside a reflecting cavity.
Superradiant axion clouds around black holes can undergo gravitational superfluorescence via a seeded coherent quadrupolar transition, leading to a detectable delayed gravitational-wave pulse.
The equilibrium radius of self-gravitating dark fermion stars is determined by the fermion mass once the total mass is given, with the Bohm potential supplying outward pressure for heavier species and inward tension for lighter ones.
Superradiant axion-like-particle clouds around rotating black holes can generate multimode squeezed graviton states with 10^6-10^7 correlated quanta showing polarization correlations and quantum-noise signatures potentially detectable by future interferometers.
Eccentric EMRIs exhibit relativistic resonances in scalar fluxes that enhance interactions with scalar clouds and amplify waveform dephasing relative to circular orbits.
A unified relativistic framework using bilinear perturbation theory calculates frequency shifts in GWs from axion clouds, handling self-interactions and multiple superradiant modes for the first time.
Time-dependent evolution of a non-rigid Nambu-Goto string around a Kerr black hole produces short-lived energy extraction followed by a propagating wave and approach to a known static configuration, with total extracted energy bounded by μM.
A one-body conformal-factor correction stabilizes boson star-black hole initial data, enabling gravitational-wave analysis that shows higher multipoles can discriminate mixed mergers from pure black-hole binaries.
Relativistic metric backreaction from scalar dark matter clouds in EMRIs produces dominant polar gravitational wave corrections for Mμ ≲ 0.12, exceeding axial and scalar radiation channels at small separations.
Superradiant amplification of charged scalar fields around rotating charged de Sitter black holes is suppressed in conformal Weyl gravity relative to general relativity, with strong exponential suppression for massive fields in the cosmological region.
Quasinormal modes correspond well to grey-body factors for vector and tensor perturbations of Schwarzschild-Tangherlini black holes in all dimensions, but fail for scalar l=2 modes in D≥7 because of multiple potential barriers.
Collective nucleon scattering in neutron-star matter suppresses the effective absorption of ultralight bosons at the long wavelengths relevant for superradiance, weakening the link between stellar cooling bounds and superradiant instability rates.
Excitation factors of long-lived quasinormal modes in horizonless compact objects scale with their small imaginary frequency, suppressing early contributions and producing a hierarchy where prompt ringdown uses ordinary modes and late echoes use cavity modes.
A novel quantity derived from GW signals encodes the density profile of dark dense environments around black holes, allowing characterization of the condensate type and DM properties via multi-wavelength observations.
Semi-analytic waveform model for scalar environments around black hole binaries is validated against numerical relativity and applied to LIGO-Virgo-KAGRA data to obtain upper limits on scalar densities with tentative evidence in GW190728.
citing papers explorer
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Stellar Superradiance and Low-Energy Absorption in Dense Nuclear Media
Collective nucleon scattering in neutron-star matter suppresses the effective absorption of ultralight bosons at the long wavelengths relevant for superradiance, weakening the link between stellar cooling bounds and superradiant instability rates.
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$\phi$-Dwarfs: White Dwarfs probe Quadratically Coupled Scalars
White dwarf mass-radius data exclude large parameter space for ultralight scalars quadratically coupled to fermions by predicting forbidden radius gaps and mass shifts toward the Chandrasekhar limit or altered maximum masses.
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No Evidence for Superradiant Axions in LIGO-Virgo-KAGRA GWTC-5 Binary Black Hole Spins
Hierarchical Bayesian analysis of GWTC-5 binary black hole spins finds no evidence for superradiant axions and excludes masses 1.7e-14 to 3.3e-12 eV at 95% CL.
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String Axiverse Enhancement of Superradiant Dark Matter Production
O(100-10^5) string axions enhance PBH superradiance efficiency via increased spin, expanding viable mass-spin regions for micro-boson star dark matter while too many axions cause overly rapid evaporation.
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Radio Emission from High-Frequency Gravitational Wave Point Sources
Radio telescopes outperform other experiments at detecting high-frequency gravitational waves from primordial black hole mergers and boson clouds through conversion to radio signals in magnetic fields.
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Constraining Ultralight Scalar Dark Matter in the Galactic Center with the S2 Orbit
Using S2 star periastron precession, the work constrains ultralight scalar dark matter mass ratios to below 10^{-3} or 1 and improves quadratic coupling bounds for masses 10^{-20} to 10^{-18} eV.
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Axions as Dark Matter, Dark Energy, and Dark Radiation
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.