We investigate thermodynamic curvatures of the Kerr and Reissner-Nordström (RN) black holes in spacetime dimensions higher than four. These black holes possess thermodynamic geometries similar to those in four dimensional spacetime. The thermodynamic geometries are the Ruppeiner geometry and the conformally related Weinhold geometry. The Ruppeiner geometry for d = 5 Kerr black hole is curved an...

We consider a black hole in a heat bath, and the whole system which consists of the black hole and the heat bath is isolated from outside environments. When the black hole evaporates, the Hawking radiation causes an energy flow from the black hole to the heat bath. Therefore, since no energy flow arises in an equilibrium state, thermodynamic state of the whole system is not in an equilibrium. T...

We postulate that supermassive black-holes grow in the centers of galaxies until they unbind the galactic gas that feeds them. We show that the corresponding self-regulation condition yields a correlation between black-hole mass (Mbh) and galaxy velocity dispersion (σ) as inferred in the local universe, and recovers the observed optical and X-ray luminosity functions of quasars at redshifts up ...

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We describe the gravitational degrees of freedom of the Schwarzschild black hole by one free variable. We introduce an equation which we suggest to be the Schrödinger equation of the Schwarzschild black hole corresponding to this model. We solve the Schrödinger equation explicitly and obtain the mass spectrum of the black hole as such as it can be observed by an observer very far away and at re...

We discuss some puzzles on the identity of black hole entropy by using the Landauer’s principle of information erasure. Especially, we discuss the information freezing on the black hole horizon in terms of information erasing process. We also calculate the quantized black hole mass spectra and entropy assuming that the black hole processes information in unit of bit. The black hole entropy gain...

Accretion disk reflection spectra, including broad iron emission lines, bear the imprints of the strong Doppler shifts and gravitational red-shifts close to black holes. The extremity of these shifts depends on the proximity of the innermost stable circular orbit to the black hole, and that orbit is determined by the black hole spin parameter. Modeling relativistic spectral features, then, give...