Accretion onto black holes in wind-fed binaries and in collapsars forms small rotating discs with peculiar properties. Such “mini-discs” accrete on the free-fall time without help of viscosity and nevertheless can have a high radiative efficiency. The inviscid mini-disc model was previously constructed for a non-rotating black hole. We extend the model to the case of a spinning black hole, calc...

We construct evolutionary models of the populations of active galactic nuclei (AGN) and supermassive black holes, in which the black hole mass function grows at the rate implied by the observed luminosity function, given assumptions about the radiative efficiency and the luminosity in Eddington units. We draw on a variety of recent X-ray and optical measurements to estimate the bolometric AGN l...

We present the results of a systematic study of the formation and evolution of binaries containing black holes and normal-star companions with a wide range of masses. We first reexamine the standard formation scenario for close black-hole binaries, where the progenitor system, a binary with at least one massive component, experienced a common-envelope phase and where the spiral-in of the compan...

Central black hole masses for 118 spiral galaxies representing morphological stages S0/a through Sc and taken from the large spectroscopic survey of Ho et al. (1997) are derived using K s-band data from 2MASS. Black hole masses are found using a calibrated black-hole – K s bulge luminosity relation, while bulge lumi-nosities are measured by means of a two-dimensional bulge/disk decomposition ro...

The destruction of the black-hole event horizon is ruled out by both cosmic censorship and the generalized second law of thermodynamics. We test the consistency of this prediction in a (more) ‘dangerous’ version of the gedanken experiment suggested by Bekenstein and Rosenzweig. A U(1)-charged particle is lowered slowly into a near extremal black hole which is not endowed with a U(1) gauge field...

We derive an exact expression for the partition function of the Euclidean BTZ black hole. Using this, we show that for a black hole with large horizon area, the correction to the Bekenstein-Hawking entropy is −3/2 log(area), in agreement with that for the Schwarzschild black hole obtained in the four dimensional canonical gravity formalism and also in a Lorentzian computation of BTZ black hole ...

We study a revised version of Witten’s 2d black hole, in which the matter and (b, c) ghosts are mixed. The level of the coset model is still 9/4. We show that this model is equivalent to that of Mukhi and Vafa, in which the level of the coset model is taken as 3, and the stress tensor is improved. We argue that the exact metric in such a model is just the semi-classical one, quite different fro...

It has been, recently pointed out that the initial value problem in new inflation models is naturally solved by supergravity effects if there exists a pre-inflation before the new inflation. We study this double inflation model in details and find that density fluctuations on small cosmological scales are much larger than those on large scales due to peculiar property of the new inflation. We s...

I discuss the effect of the formation of a black hole on a (close) binary and show some of the current constraints that the observed properties of black hole X-ray binaries put on the formation of black holes. In particular I discuss the evidence for and against asymmetric kicks imparted on the black hole at formation and find contradicting answers, as there seems to be evidence for kick for in...

We derive and solve the black hole attractor conditions of N = 8 supergravity by finding the critical points of the corresponding black hole potential. This is achieved by a simple generalization of the symplectic structure of the special geometry to all extended supergravities with N > 2. There are two classes of solutions for regular black holes, one for 1/8 BPS ones and one for the non-BPS. ...