A wave impinging on a Kerr black hole can be amplified as it scatters off the if certain conditions are satisfied, giving rise to superradiant scattering. By placing mirror around one make system unstable. This is black-hole bomb of Press and Teukolsky. We investigate in detail this process compute growing time scales oscillation frequencies function mirror's location. It found that order for plus become unstable there minimum distance at which must located. also give an explicit example...

The wide applications of higher dimensional gravity and gauge/gravity duality have fuelled the search for new stationary solutions Einstein equation (possibly coupled to matter). In this topical review, we explain mathematical foundations give a practical guide numerical solution gravitational boundary value problems. We present these methods by way example: resolving asymptotically flat black rings, singly spinning lumpy holes in anti-de Sitter (AdS), Gregory–Laflamme zero modes small...

Superradiance in black hole spacetimes can trigger instabilities. Here we show that, due to superradiance, small Kerr--anti-de Sitter holes are unstable. Our demonstration uses a matching procedure, long wavelength approximation.

Gravitational wave solutions to Einstein's equations and their generation are examined in D-dimensional flat spacetimes. First the plane analyzed; then is studied with solution for metric tensor being obtained help of retarded Green's functions. Because difficulties handling tails odd dimensions we concentrate our study on even dimensions. We compute quantities zone terms energy-momentum at time. Some special cases interest studied. slow motion approximation, where quadrupole formula...

Bizon and Rostworowski have recently suggested that anti-de Sitter spacetime might be nonlinearly unstable to transfering energy smaller scales eventually forming a small black hole. We consider pure gravity with negative cosmological constant find strong support for this idea. While one can start single linearized mode add higher order corrections construct nonlinear geon, is not possible starting linear combination of two or more modes. One forced frequency modes growing amplitude. The...

It has been conjectured that higher-dimensional rotating black holes become unstable at a sufficiently large value of the rotation, and new with pinched horizons appear threshold instability. We search numerically find stationary axisymmetric perturbations Myers-Perry single spin mark onset instability appearance hole phases. also ultraspinning Gregory-Laflamme instabilities strings branes.

Despite the recent evidence that anti-de Sitter (AdS) spacetime is nonlinearly unstable, we argue many asymptotically AdS solutions are stable. This includes geons, boson stars and black holes. As part of our argument, calculate frequencies long-lived gravitational quasinormal modes holes in various dimensions. We also discuss a new class describing noncoalescing hole binaries.

A bstract We use a mix of analytic and numerical methods to exhaustively study class asymptotically global AdS solitons hairy black hole solutions in negative cosmological constant Einstein Maxwell gravity coupled charged massless scalar field. Our results depend sensitively on the charge e The solitonic branch we hits Chandrashekhar limit at finite mass small , but extends arbitrarily large larger . At low values no holes exist. intermediate exist above critical charge. all lowest is smooth...

Recent work indicates that the strong cosmic censorship hypothesis is violated by nearly extremal Reissner--Nordstr\"om--de Sitter black holes. It was argued perturbations of such a hole decay sufficiently rapidly perturbed spacetime can be extended across Cauchy horizon as weak solution equations motion. In this paper we consider case Kerr--de We find that, for any nonextremal value parameters, there are quasinormal modes which slowly to ensure respected. Our analysis covers both scalar...

Black holes in anti-de Sitter (AdS) backgrounds play a pivotal role the gauge/gravity duality where they determine, among other things, approach to equilibrium of dual field theory. We undertake detailed analysis perturbed Kerr-AdS black four- and five-dimensional spacetimes, including computation its quasinormal modes, hydrodynamic modes superradiantly unstable modes. Our results shed light on possibility new hole phases with single Killing field, possible holographic phenomena presence...

It has been argued that the strong cosmic censorship conjecture is violated by Reissner-Nordstr\"om-de Sitter black holes: for near-extremal holes, generic scalar field perturbations arising from smooth initial data have finite energy at Cauchy horizon even though they are not continuously differentiable there. In this paper, we consider analogous problem coupled gravitational and electromagnetic perturbations. We find such exhibit a much worse violation of censorship: sufficiently large...

Ultralight bosons and axion-like particles appear naturally in different scenarios could solve some long-standing puzzles. Their detection is challenging, all direct methods hinge on unknown couplings to the Standard Model of particle physics. However, universal coupling gravity provides model-independent signatures for these fields. We explore here superradiant instability spinning black holes triggered presence such The taps angular momentum from limits maximum spin astrophysical holes....

It has been shown recently that the strong cosmic censorship conjecture is violated by near-extremal Reissner–Nordström–de Sitter black holes. We investigate whether introduction of a charged scalar field can rescue censorship. find such improves situation but there always neighbourhood extremality in which perturbations arising from smooth initial data.

We construct a template to model the post-merger phase of binary black hole coalescence in presence remnant $U(1)$ charge. include quasi-normal modes typically dominant during coalescence, $(\ell,m,n) = \{(2,2,0), (2,2,1)\}$ and also present analytical fits for quasinormal mode frequencies Kerr-Newman terms its spin charge, here including $(3,3,0)$ mode. Aside from astrophysical electric our can accommodate extensions Standard Model, such as dark photon. Applying LIGO-Virgo detections, we...

Because of coherent superradiant amplification, massive bosonic fields can trigger an instability in spinning black holes, tapping their energy and angular momentum forming macroscopic Bose-Einstein condensates around them. This phenomenon produces gaps the mass-spin distribution astrophysical a continuous gravitational-wave signal emitted by condensate, several environmental effects relevant for astronomy radio images holes. While spectrum superradiantly unstable mode is known great detail...

A wave impinging on a Kerr black hole can be amplified as it scatters off the if certain conditions are satisfied giving rise to superradiant scattering. By placing mirror around one make system unstable. This is bomb of Press and Teukolsky. We investigate in detail this process compute growing timescales oscillation frequencies function mirror's location. It found that order for plus become unstable there minimum distance at which must located. also give an explicit example showing such...

It is now established that small Kerr-Anti-de Sitter (Kerr-AdS) black holes are unstable against scalar perturbations, via superradiant amplification mechanism. We show Kerr-AdS also gravitational perturbations and we compute the features of this instability. describe with great detail evolution In particular, identify its endpoint state. corresponds to a hole whose boundary an Einstein universe rotating light velocity. This expected be slightly oblate co-exist in equilibrium certain amount...

We provide strong evidence that, up to 99.999% of extremality, Kerr-Newman black holes (KNBHs) are linear mode stable within Einstein-Maxwell theory. derive and solve, numerically, a coupled system two partial differential equations for gauge invariant fields that describe the most general perturbations KNBH. determine quasinormal (QNM) spectrum KNBH as function its three parameters find no unstable modes. In addition, we lowest radial overtone QNMs connected continuously gravitational ℓ=m=2...

A bstract We investigate the stability of inner horizon a rotating BTZ black hole. show that linear perturbations arising from smooth initial data are arbitrarily differentiable at if hole is sufficiently close to extremality. This demonstrated for scalar fields, massive Chern-Simons Proca and spin-2 fields. Thus strong cosmic censorship conjecture violated by near-extremal in large class theories. However, we weaker \rough" version respected. calculate renormalized energymomentum tensor...

We study the gravito-electromagnetic perturbations of Kerr-Newman (KN) black hole and identify two---photon sphere near-horizon---families quasinormal modes (QNMs) hole, computing frequency spectra (for all KN parameter space) with slowest decay rate. uncover a novel phenomenon for QNMs that is unique to system, namely eigenvalue repulsion between QNM families. Such feature common in solid state physics where e.g., it responsible energy bands/gaps electrons moving certain Schr\"odinger...

The anti--de Sitter C metric (AdS metric) is characterized by a quite interesting new feature when compared with the in flat or de backgrounds. Indeed, contrary to what happens these two last exact solutions, AdS only describes pair of accelerated black holes if acceleration parameter satisfies $A>1/\mathcal{l},$ where $\mathcal{l}$ cosmological length. cannot interact gravitationally and their totally provided pressure exerted strut that pushes apart. Our analysis based on study causal...

Recently certain nonsupersymmetric solutions of type IIb supergravity were constructed [V. Jejjala, O. Madden, S. F. Ross, and G. Titchener, Phys. Rev. D 71, 124030 (2005).], which are everywhere smooth, have no horizons thought to describe non-Bogomolnyi-Prasad-Sommerfield microstates the D1-D5 system. We demonstrate that these all classically unstable. The instability is a generic feature horizonless geometries with an ergoregion. consider end point this argue decay supersymmetric...