Superradiance — the 2020 Edition. (arXiv:1501.06570v7 [gr-qc] UPDATED)

<a href="http://arxiv.org/find/gr-qc/1/au:+Brito_R/0/1/0/all/0/1">Richard Brito</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Cardoso_V/0/1/0/all/0/1">Vitor Cardoso</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Pani_P/0/1/0/all/0/1">Paolo Pani</a>

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.

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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