Interior of black holes and information recovery

International Journal of Modern Physics A, 2015

We discuss a sufficiently large four-dimensional Schwarzschild black hole which is in equilibrium with a heat bath. In other words, we consider a black hole which has grown up from a small one in the heat bath adiabatically. We express the metric of the interior of the black hole in terms of two functions: One is the intensity of the Hawking radiation, and the other is the ratio between the radiation energy and the pressure in the radial direction. Especially in the case of conformal matters we check that it is a self-consistent solution of the semiclassical Einstein equation, Gμν = 8πG〈Tμν〉. It is shown that the strength of the Hawking radiation is proportional to the c-coefficient, that is, the coefficient of the square of the Weyl tensor in the four-dimensional Weyl anomaly.

Physical review, 2019

A coherent picture of the quantum mechanics of a collapse-formed, evaporating black hole is presented. In a distant frame, semiclassical theory in the zone describes microscopic dynamics of only the "hard modes," the modes that are hard enough to be discriminated in the timescale of Hawking emission. The thermal nature of these modes arises from microcanonical typicality of the full black hole degrees of freedom, mostly composed of the "soft modes," the modes that cannot be discriminated at the semiclassical level. The hard modes are purified by a combined system of the soft modes and early Hawking radiation but not by either of them separately. This intrinsically tripartite structure of entanglement is general, regardless of the age of the black hole. The interior spacetime emerges only at a coarse-grained level. To describe it, an effective theory can be erected at each time, which applies only to a limited spacetime region determined by the time at which the theory is erected. The entire interior of the black hole can be described only using multiple effective theories erected at different times, realizing the idea of complementarity. We analyze the implications of the entanglement structure described here for various phenomena, including Hawking evaporation and general information retrieval. For multiple entangled black holes, it implies that semiclassical objects dropped into different black holes cannot meet in the interior, although each object smoothly enters the horizon of the black hole to which it is falling. We also discuss physics in Rindler space, elucidating how it is obtained as a smooth limit of the black hole physics.

Universe, 2017

We analyze the time evolution of a spherically-symmetric collapsing matter from the point of view that black holes evaporate by nature. We consider conformal matters and solve the semi-classical Einstein equation G µν = 8πG T µν by using the four-dimensional Weyl anomaly with a large c coefficient. Here, T µν contains the contribution from both the collapsing matter and Hawking radiation. 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.

Mod.Phys.Lett. A27 (2012) 12501, 2012

For more than 30 years the discovery that black holes radiate like black bodies of specific temperature has triggered a multitude of puzzling questions concerning their nature and the fate of information that goes down the black hole during its lifetime. The most tricky issue in what is known as information loss paradox is the apparent violation of unitarity during the formation/evaporation process of black holes. A new idea is proposed based on the combination of our knowledge on Hawking radiation as well as the Einstein-Podolsky-Rosen phenomenon, that could resolve the paradox and spare physicists from the unpalatable idea that unitarity can ultimately be irreversibly violated even under special conditions.

2005

The formation and evaporation of a black hole can be viewed as a scattering process in Quantum Gravity. Semiclassical arguments indicate that the process should be non-unitary, and that all the information of the original quantum state forming the black hole should be lost after the black hole has completely evaporated, except for its mass, charge and angular momentum. This would imply a violation of basic principles of quantum mechanics. We review some proposed resolutions to the problem, including developments in string theory and a recent proposal by Hawking. We also suggest a novel approach which makes use of some ingredients of earlier proposals. [Based on Talks given at ERE2004 "Beyond General Relativity", Miraflores de la Sierra, Madrid (Sept 2004), and at CERN (Oct 2004)].

International Journal of Modern Physics A, 2013

We construct a self-consistent model which describes a black hole from formation to evaporation including the backreaction from the Hawking radiation. In the case where a null shell collapses, at the beginning the evaporation occurs, but it stops eventually, and a horizon and singularity appear. On the other hand, in the generic collapse process of a continuously distributed null matter, the black hole evaporates completely without forming a macroscopically large horizon nor singularity. We also find a stationary solution in the heat bath, which can be regarded as a normal thermodynamic object.

Classical and Quantum Gravity, 2005

A paradigm describing black hole evaporation in non-perturbative quantum gravity is developed by combining two sets of detailed results: i) resolution of the Schwarzschild singularity using quantum geometry methods [1, 2]; and ii) time-evolution of black holes in the trapping and dynamical horizon frameworks [3, 4, 5, 6]. Quantum geometry effects introduce a major modification in the traditional space-time diagram of black hole evaporation, providing a possible mechanism for recovery of information that is classically lost in the process of black hole formation. The paradigm is developed directly in the Lorentzian regime and necessary conditions for its viability are discussed. If these conditions are met, much of the tension between expectations based on space-time geometry and structure of quantum theory would be resolved.

Physics Letters B, 1999

By extending the charged Vaidya metric to cover all of spacetime, we obtain a Penrose diagram for the formation and evaporation of a charged black hole.

Physical Review D, 2007

We study the formation of black holes by spherical domain wall collapse as seen by an asymptotic observer, using the functional Schrodinger formalism. To explore what signals such observers will see, we study radiation of a scalar quantum field in the collapsing domain wall background. The total energy flux radiated diverges when backreaction of the radiation on the collapsing wall is ignored, and the domain wall is seen by the asymptotic observer to evaporate by non-thermal "pre-Hawking radiation" during the collapse process. Evaporation by pre-Hawking radiation implies that an asymptotic observer can never lose objects down a black hole. Together with the non-thermal nature of the radiation, this may resolve the black hole information loss problem.

Journal of High Energy Physics

The near-horizon geometry of evaporation black holes is determined according to the semi-classical Einstein equation. We consider spherically symmetric configurations in which the collapsing star has already collapsed below the Schwarzschild radius. The back-reaction of the vacuum energy-momentum, including Hawking radiation, is taken into account. The vacuum energy-momentum plays a crucial role in a small neighborhood of the apparent horizon, as it appears at the leading order in the semi-classical Einstein equation. Our study is focused on the time-dependent geometry in this region.