We study the thermodynamic stability of charged black holes in gauged supergravity theories in D = 5, D = 4 and D = 7. We find explicitly the location of the Hawking-Page phase transition between charged black holes and the pure anti-de Sitter space-time, both in the grand-canonical ensemble, where electric potentials are held fixed, and in the canonical ensemble, where total charges are held f...

We have developed a new numerical code to study the evolution of distorted, rotating black holes. We discuss the numerical methods and gauge conditions we developed to evolve such spacetimes. The code has been put through a series of tests, and we report on (a) results of comparisons with codes designed to evolve non-rotating holes, (b) evolution of Kerr spacetimes for which analytic properties...

Emperor penguins leap from the water onto the sea ice. Their ability to reach above-water height depends critically on initial vertical speed of their leaping, assuming that the kinetic energy is converted to gravitational potential energy. We deliberately changed the above-water heights of ice hole exits, in order to examine whether penguins adjusted swim speed in accordance with the above-wat...

We use deep HST/ACS F555W and F814W photometry of resolved stars in the M81 Group dwarf irregular galaxy Ho II to study the hypothesis that the holes identified in the neutral ISM (HI) are created by stellar feedback. From the deep photometry, we construct color-magnitude diagrams (CMDs) and measure the star formation histories (SFHs) for stars contained in HI holes from two independent holes c...

We review recent progress in our understanding of the physics of black holes. In particular, we discuss the ideas from string theory that explain the entropy of black holes from a counting of microstates of the hole, and the related derivation of unitary Hawking radiation from such holes.

Using the quasi-normal modes frequency of extremal Reissner-Nordström black holes, we obtain area spectrum for these type of black holes. We show that the area and entropy black hole horizon are equally spaced. Our results for the spacing of the area spectrum differ from that of schwarzschild black holes. ∗E-mail: [email protected]