Quantum Black Holes in the Sky?
We analyze the time evolution of a spherically-symmetric collapsing matter from the point of view that black holes evaporate by nature. We obtain a self-consistent solution of the semi-classical Einstein equation. The solution indicates that the collapsing matter forms a dense object and evaporates without horizon or singularity, and it has a surface but looks like an ordinary black hole from the outside. Any object we recognize as a black hole should be such an object.
A quantum system behaves classically when quantum probabilities are high for coarse-grained histories correlated in time by deterministic laws. That is as true for the flight of a tennis ball as for the behavior of spacetime geometry in gravitational collapse. Classical spacetime may be available only in patches of configuration space with quantum transitions between them. Global structures of general relativity. such as event horizons may not be available.
Postulates are given for a quantum-gravitational description of black holes, that include correspondence with a quantum field theory description for freely falling observers crossing the horizon. These lead to “soft gravitational structure,” which can transfer information to outgoing radiation either with or without large metric perturbations. Prospects for observing such departures from the standard field-theoretic description of black holes will be briefly discussed.
: Astrophysical black hole candidates might be horizonless ultra-compact objects. Of particular interest is the plausible fundamental connection with quantum gravity. The puzzle is then why we shall expect Planck scale corrections around the horizon of a macroscopic black hole.
The standard way to understand quantum corrected black holes leads to the information loss paradox and the lifetime dilemma. A radical way out of this situation is to give up a hypothesis which is tacitly assumed in the vast majority of works on the subject: that the classical singularity is substituted by something effectively acting as a sink for a long period of time, as seen by asymptotic observers.
Eliminating this characteristic changes drastically much of the physics now associated to black holes. A nice feature of the new hypothesis it that it offers a
The internal structure of extremal and near-extremal black holes in string theory involves a variety of ingredients — strings and branes — that lie beyond supergravity, yet it is often difficult to achieve quantitative control over these ingredients in a regime where the state being described approximates a black hole. The supertube is a brane bound state that has been proposed as a paradigm for how string theory resolves black hole horizon structure. This talk will describe how the worldsheet dynamics of strings can be solved exactly in a wide variety of supertube backgrounds, opening up
Black holes appear to lead to information loss, thus violating one of the fundamental tenets of Quantum Mechanics. Recent Information-Theory-based arguments imply that information loss can only be avoided if at the scale of the black hole horizon there exists a structure (commonly called fuzzball or
The black hole information paradox poses a serious difficulty for theoretical physics. Over the last two decades there has emerged a resolution to this paradox in string theory, based on the discovery that heavy states in string theory swell up into horizon sized "fuzzballs". The talk will review the fuzzball construction and how the traditional semiclassical expectation of a vacuum horizon gets violated.