Related papers: Numerical investigation of plasma-driven superradi…
Dwarf galaxies and globular clusters may contain intermediate mass black holes ($10^{3}$ to $10^{5}$ solar masses) in their cores. Estimates of ~$10^{3}$ neutron stars in the central parsec of the Galaxy and similar numbers in small…
It has long been believed that accretion onto supermassive black holes powers quasars, but there has been relatively few observational constraints on the spins of the black holes. We address this problem by estimating the average radiative…
Accreting black holes in galactic X-ray sources are surrounded by hot plasma. The innermost part of these systems is likely a corona with different temperatures for ions and electrons. In the so-called low-hard state, hot electrons…
A scenario is put forth for the formation of supermassive black holes at the centers of galaxies. It depends upon the formation of a Mestel disk with a flat rotation curve, where the mass is proportional to r and thickness to 1/r. Such…
Super-Eddington accretion discs with 3 and 15 dot M_E around black holes with mass 10 M_sun are examined by two-dimensional radiation hydrodynamical calculations extending from the inner disc edge to 5*10^4 r_g and lasting up to \sim 10^6…
We consider the imprint of superradiant instabilities of nonevaporating primordial black holes (PBHs) on the spectrum of the cosmic microwave background (CMB). In the radiation dominated era, PBHs are surrounded by a roughly homogeneous…
Accretion disks around active galactic nuclei are potentially unstable to star formation at large radii. We note that when the compact objects formed from some of these stars spiral into the central supermassive black hole, there is no…
Under some conditions, light boson fields grow exponentially around a rotating black hole, called the superradiance instability. We discuss effects of nonlinear interactions of the boson on the instability. In particular, we focus on the…
The peaks of the spectra of the accretion disks surrounding massive black holes in quasars are in the far-UV or soft X-ray band, which are usually not observed. However, in the disk corona model, the soft photons from the disk are…
A solid theoretical understanding of how inflowing, accreting plasma around black holes and other compact objects gives rise to outflowing winds and jets is still lacking, despite decades of observations. The fact that similar processes and…
The instability of rotating Kerr black holes due to massive scalar perturbations is investigated. It is well known that a bosonic field impinging on a Kerr black hole can be amplified as it scatters off the hole. This superradiant…
Sufficient conditions are found on the ion velocity distribution $f_i$ and potential amplitude for stability of steady electron holes moving at slow speeds, coinciding with the bulk of $f_i$. Fully establishing stability requires…
In extreme/intermediate-mass-ratio inspirals (E/IMRIs) embedded in dark-matter (DM) spikes, the secondary black hole can accrete collisionless particles from the surrounding halo. We study how the companion's spin controls this process, and…
Black holes provide a natural laboratory to study particle physics and astrophysics. When black holes are surrounded by matter fields, there will be plenty of phenomena which can have observational consequences, from which we can learn…
Cosmic-ray streaming instabilities at supernova shocks are discussed in the quasilinear diffusion formalism which takes into account the feedback effect of wave growth on the cosmic ray streaming motion. In particular, the nonresonant…
Plasma instabilities can be encountered in many branches of physics. This work focuses on relativistic plasmas with applications in theoretical astrophysics and particle accelerator physics. Even though these fields seem to be unrelated the…
This paper investigates the dynamical behavior of steady spherical accretion onto a static, magnetically charged black hole embedded in a perfect fluid dark matter (PFDM) background. Using the shadow observations of M87* from the Event…
We numerically investigate the dynamics of a 2D non-magnetised protoplanetary disc surrounded by an inflow coming from an external envelope. We find that the accretion shock between the disc and the inflow is unstable, leading to the…
We consider constraints on the axion-photon coupling by superradiance due to a plasma instability in the magnetospheres of millisecond pulsars. We compute the growth rate of a superradiant axion cloud in a dipole magnetic field, and give a…
The propagation of very-high-energy gamma-rays (VHEGRs) in the extragalactic space offers the opportunity to study astrophysical phenomena not reproducible in laboratories. In particular, the deviation from predictions of the observed…