Related papers: Black Holes of Negative Mass
Recently, two of us have argued that non-Kerr black holes in gravity theories different from General Relativity may have a topologically non-trivial event horizon. More precisely, the spatial topology of the horizon of non-rotating and…
We describe some specific quantum black hole model. It is pointed out that the origin of a black hole entropy is the very process of quantum gravitational collapse. The quantum black hole mass spectrum is extracted from the mass spectrum of…
Black holes are an apparently unavoidable prediction of classical General Relativity, at least if matter obeys the strong energy condition rho + 3p > 0. However quantum vacuum fluctuations generally violate this condition, as does the eq.…
Black holes represent outstanding astrophysical laboratories to test the strong gravity regime, since alternative theories of gravity may predict black hole solutions whose may differ distinctly from those of General Relativity. When higher…
In this work the quantum gravitational equations are derived by using the quantum hydrodynamic description. The outputs of the work show that the quantum dynamics of the mass distribution inside a black hole can hinder its formation if the…
We examine spherical gravitational collapse of a matter model with vanishing radial pressure and non-zero tangential pressure. It is seen analytically that the collapsing cloud either forms a black hole or disperses depending on values of…
Supersymmetric String theories find occurrences of extremal Black Holes with gravitational mass M=Q where Q is the charge (G=c=1). Thus, for the chargeless cases, they predict M=0. We show that General Theory of Relativity, too, demands a…
We argue that black holes admit vortex structure. This is based both on a graviton-condensate description of a black hole as well as on a correspondence between black holes and generic objects with maximal entropy compatible with unitarity,…
We investigate here the genericity and stability aspects for naked singularities and black holes that arise as the final states for a complete gravitational collapse of a spherical massive matter cloud. The form of the matter considered is…
Black holes with masses $\approx 1\, M_{\odot}$ cannot be produced via stellar evolution. A popular scenario of their formation involves transmutation of neutron stars - by accumulation of dark matter triggering gravitational collapse in…
A theory of quantum gravity is expected to change profoundly our understanding of black holes. Quantum theory has already shown, as a first approximation, that a black hole slowly evaporates. Non-perturbative quantum gravity also predicts…
We uncover two mechanisms that can render Kerr black holes unstable in scalar-tensor gravity, both associated to the presence of matter in the vicinity of the black hole and the fact that this introduces an effective mass for the scalar.…
We consider general relativistic homogeneous gravitational collapses for dust and radiation. We show that replacing the density profile with an effective density justified by some quantum gravity framework leads to the avoidance of the…
Several anomalies of black hole thermodynamics are resolved if one accepts hints from semi classical theory that in regions of strong gravity the energy density of the vacuum can become substantially negative. This leads to a picture of the…
The new, rapidly developing field of theoretical research --- studies of dark energy interacting with black holes (and, in particular, accreting onto black holes) --- is reviewed. The term `dark energy' is meant to cover a wide range of…
Aspects of the thermo-dynamics of a black hole which is either pierced by a cosmic gauge string or contains a global monopole are investigated. We also make some comments on the physical significance of the fact that the gravitational mass…
A definition of a Newtonian black hole is possible which incorporates the mass-energy equivalence from special relativity. However, exploiting a double spherical shell model, it will be shown that the ensuing gravitational self-energy and…
Starting from the Oppenheimer-Snyder model, we know how in classical general relativity the gravitational collapse of matter form a black hole with a central spacetime singularity. It is widely believed that the singularity must be removed…
We solve dynamical equations of motion to determine the conditions under which an over-dense region in the early universe will lead to collapse to a black hole, starting from horizon crossing of the over-dense region to the point of…
When two point particles, coupled to three dimensional gravity with a negative cosmological constant, approach each other with a sufficiently large center of mass energy, then a BTZ black hole is created. An explicit solution to the…