Related papers: Black Holes under External Influence
We discuss how cosmic strings can be used to mine energy from black holes. A string attached to the black hole gives rise to an additional channel for the energy release. It is demonstrated that when a string crosses the event horizon, its…
Astrophysical black holes do not exist in vacuum, and their motion is affected by the galactic environment. As a black hole moves it attracts stars and matter, creating a wake that, in turn, exerts an effective friction slowing down the…
Black holes represent extreme conditions of physical laws. Being predicted about a century ago, they are now accepted as astrophysical reality by most of the scientific community. Only recently more direct evidence of their existence has…
We consider the inward propagation of warping and eccentric disturbances in discs around black holes under a wide variety of conditions. In our calculations we use secular theories of warped and eccentric discs and assume the deformations…
An analysis of cosmic string breaking with the formation of black holes attached to the ends reveals a remarkable feature: the black holes can be correlated or uncorrelated. We find that, as a consequence, the number-of-states enhancement…
In backgrounds with compact dimensions there may exist several phases of black objects including the black-hole and the black-string. The phase transition between them raises puzzles and touches fundamental issues such as topology change,…
What is meant by the "inner edge" of an accretion disk around a black hole depends on the property that defines the edge. We discuss four such definitions using data from recent high-resolution numerical simulations. These are: the…
Black hole entropy is shown to be a consequence of restricting our description of physics to the exterior of black holes. This precludes the need for a statistical mechanical description of this entropy in terms of microstates.
It is proved that spherically symmetric extermal black holes possess at least one external light ring. Our remarkably compact proof is based on the dominant energy condition which characterizes the external matter fields in the non-vacuum…
We find all the classical solutions (minimal surfaces) of open or closed strings in {\it any} two dimensional curved spacetime. As examples we consider the SL(2,R)/R two dimensional black hole, and any 4D black hole in the Schwarzschild…
Quantum aspects of black holes represent an important testing ground for a theory of quantum gravity. The recent success of string theory in reproducing the Bekenstein-Hawking black hole entropy formula provides a link between general…
Black hole solutions can be used to shed light on general issues in General Relativity and Quantum Physics. Black--hole hair, entropy and naked singularities are considered here, along with some implications for the inflationary universe…
Our understanding of space and time is probed to its depths by black holes. These objects, which appear as a natural consequence of general relativity, provide a powerful analytical tool able to examine macroscopic and microscopic…
The study of black holes in string theory has led to the discovery of deep and surprising connections between black holes and modular forms -- which are two classical, a priori unrelated, subjects. This article explains the main physical…
A complex scalar field on a charged black hole in a cavity is known to experience a superradiant instability. We investigate possible final states of this instability. We find hairy black hole solutions of a fully coupled system of Einstein…
We consider electromagnetic fields and charged particle dynamics around non-singular black holes in conformal gravity immersed in an external, asymptotically uniform magnetic field. First, we obtain analytic solutions of the electromagnetic…
Black holes in several dimensions and in several theories are studied and discussed. The theories are, general relativity, Kaluza-Klein, Brans-Dicke, Lovelock gravity and string theory.
The spin of a black hole is an important quantity to study, providing a window into the processes by which a black hole was born and grew. Further, spin can be a potent energy source for powering relativistic jets and energetic particle…
We study the propagation of the quantum field perturbations in the interior of the Schwarzschild black hole. The interior of the black hole is like an anisotropic cosmological background which expands in one extended direction while…
In this work we derive simple closed-form expressions for the dynamical friction acting on black holes moving through ultralight (scalar field) dark matter, covering both non-relativistic and relativistic black hole speeds. Our derivation…