Mengjie Wang

Marginal scalar and Proca clouds around Reissner-Nordstr\"om black holes

Massive scalar test fields around Kerr black holes can form quasi-bound states with complex frequencies. Some of these states decay in time, but some others -- in the superradiant regime -- grow, causing a superradiant instability. Precisely at the threshold between decaying and growing modes, there exist bound states with real frequency, known as scalar clouds. Fully non-linear counterparts of these clouds have been shown to yield Kerr black holes with scalar hair. Here, we consider massive, (electrically) charged, test scalar and Proca fields on the background of Reissner-Nordstrom black holes. By computing the quasi-bound state frequencies, we establish that no such states exist in the superradiant regime for the Proca field -- a similar behavior to that known for scalar fields. But decaying quasi-bound states with an arbitrarily small imaginary part of the frequency exist and thus which are arbitrarily long lived. In the limit of vanishing imaginary part of the frequency, the field does not trivialize and we dub the corresponding configurations as marginal (charged) scalar or Proca clouds, since they are only marginally bound. We comment on the possible existence of non-linear counterparts to these marginal clouds.

Hawking radiation for a Proca field in D-dimensions

We study the wave equation of a massive vector boson in the background of a

Maxwell perturbations on asymptotically anti–de Sitter spacetimes: Generic boundary conditions and a new branch of quasinormal modes

D

n-DBI gravity, maximal slicing, and the Kerr geometry

-dimensional Schwarzschild black hole. The mass term introduces a coupling between two physical degrees of freedom of the field, and we solve the resulting system of ordinary differential equations numerically, without decoupling. We show how to define decoupled transmission factors from an

Dirac perturbations on Schwarzschild–anti–de Sitter spacetimes: Generic boundary conditions and new quasinormal modes

\mathbf{S}

Hawking radiation for a Proca field in D dimensions. II. charged field in a brane charged black hole

matrix and compute them for various modes, masses, and space-time dimensions. The mass term lifts the degeneracy between transverse modes, in

Hawking Radiation for a Proca Field: Numerical Strategy

D=4

Maxwell perturbations on Kerr–anti–de Sitter black holes: Quasinormal modes, superradiant instabilities, and vector clouds

, and excites the longitudinal modes, in particular, the

Superradiant instabilities in a D-dimensional small Reissner-Nordström-anti-de Sitter black hole

s

Hawking Radiation for a Proca Field: the Coupled Modes

wave. Moreover, it increases the contribution of waves with larger