Information Loss in General Relativity-G. t 'Hooft

General Relativity and Gravitation, 2010

The trans-Planckian and information loss problems are usually discussed in the literature as separate issues concerning the nature of Hawking radiation. Here we instead argue that they are intimately linked, and can be understood as "two sides of the same coin" once it is accepted that general relativity is an effective field theory.

2010

We review the different options for resolution of the black hole loss of information problem. We classify them first into radical options, which require a quantum theory of gravity which has large deviations from semi-classical physics on macroscopic scales, such as non-locality or endowing horizons with special properties not seen in the semi-classical approximation, and conservative options, which do not need such help. Among the conservative options, we argue that restoring unitary evolution relies on elimination of singularities. We argue that this should hold also in the AdS/CFT correspondence.

Nuclear Physics B - Proceedings Supplements, 1995

In these lectures, the author's point of view on the problem of Hawking Evaporation of Black Holes is explained in some detail. A possible resolution of the information loss paradox is proposed, which is fully in accord with the rules of quantum mechanics. Black hole formation and evaporation leaves over a remnant which looks pointlike to an external observer with low resolving power, but actually contains a new infinite asymptotic region of space. Information can be lost to this new region without violating the rules of quantum mechanics. However, the thermodynamic nature of black holes can only be understood by studying the results of measurements that probe extremely small (sub-Planck scale) distances and times near the horizon. Susskind's description of these measurements in terms of string theory may provide an understanding of the Bekenstein-Hawking (BH) entropy in terms of the states of stranded strings that cross the horizon. The extreme nonlocality of string theory when viewed at short time scales allows one to evade all causality arguments which pretend to prove that the information encoded in the BH entropy can only * Lectures given at the Spring School on Supersymmetry, Supergravity, and Superstrings, Trieste, March 1994. Supported in part by the Department of Energy under grant No. DE-FG05-90ER40559. be accessed by the external observer in times much longer than the black hole evaporation time. The present author believes however that the information lost in black hole evaporation is generically larger than the BH entropy, and that the remaining information is causually separated from the external world in the expanding horn of a black hole remnant or cornucopion. The possible observational signatures of such cornucopions are briefly discussed.

arXiv (Cornell University), 2022

Thirty years ago, John Preskill [1] concluded "that the information loss paradox may well presage a revolution in fundamental physics" and mused that "Conceivably, the puzzle of black hole evaporation portends a scientific revolution as sweeping as that that led to the formulation of quantum theory in the early 20th century." Many still agree with this assessment. On the other hand, it seems to me the "paradox" has little to do with the physical world but rather, at best, simply points out the possible inconsistency of two, already disparate, theories (mathematical models) of nature, general relativity and quantum mechanics, with virtually no conceivable observational consequences. The information paradox hinges on the concepts of a pure quantum state, the unitarity of quantum mechanics, and Hawking's semi-classical calculation of black hole evaporation. I used the qualifier "at best" above because, for me, the concept of a quantum state is far more restrictive than required by the paradox while unitarity is not a property of nature but rather of a mathematical model and is certainly already violated by the process of making a measurement. Furthermore, the semi-classical calculation of Hawking is surely of limited applicability. Disclaimer: I am an experimental physicist (now retired) and am ill-equipped to delve into the theoretical details of the black hole information paradox. At heart, I'm an empiricist and pragmatic to a fault. While I marvel at and have great respect for the wonderful mathematical models created by theorists, in the absence of observations my interest in them quickly wanes. In the last paragraph of Preskill's essay quoted above, he likewise expresses a "devout wish…that experiment can guide us"; however, in its absence, he muses, "…it is not so unrealistic to hope to make real progress via pure thought." As you might imagine, this is not my sentiment for how physics evolves. With this in mind, the purpose of my present essay is not to shed light on the information paradox but rather to explain my lack of interest in it.

Physical Review D, 1993

The purpose of this paper is to analyse, in the light of information theory and with the arsenal of (elementary) quantum mechanics (EPR correlations, copying machines, teleportation, mixing produced in subsystems owing to a trace operation, etc.) the scenarios available on the market to resolve the so-called black-hole information paradox. We shall conclude that the only plausible ones are those where either the unitary evolution of quantum mechanics is given up, in which information leaks continuously in the course of black-hole evaporation through non-local processes, or those in which the world is polluted by an infinite number of meta-stable remnants.

Foundations of Physics, 2018

We discuss some recent work by Tim Maudlin concerning Black Hole Information Loss. We argue, contra Maudlin, that there is a paradox, in the straightforward sense that there are propositions that appear true, but which are incompatible with one another. We discuss the significance of the paradox and Maudlin's response to it.

Int.J.Theor.Math.Phys. 2N2 (2012) 5-9, 2012

The discovery that black holes emit thermal type radiation changed radically our perception of their behavior sinve it means that some amount of information eventually returns to the universe outside the black hole. Then rises the question whether it is the whole of this information that goes back to the universe during the black hole evaporation or not. Numerous theories supporting either information preservation or extinction have been developed ever since. A new idea is proposed, based on a deep re-examination of what information is and what are its properties. We postulate that not all kinds of information are of equal importance to nature and, as a result, some of them should be preserved under any conditions, while the rest are allowed to be destroyed, so both preservation and destruction of information is what actually happens during the black hole formation/evaporation process.

Proceedings of the Conference in Honour of the 90th Birthday of Freeman Dyson, 2014

Physical Review Letters, 2007

Can quantum-information theory shed light on black-hole evaporation? By entangling the in-fallen matter with an external system we show that the black-hole information paradox becomes more severe, even for cosmologically sized black holes. We rule out the possibility that the information about the infallen matter might hide in correlations between the Hawking radiation and the internal states of the black hole. As a consequence, either unitarity or Hawking's semiclassical predictions must break down. Any resolution of the black-hole information crisis must elucidate one of these possibilities.

General Relativity and Gravitation, 2015

The two-point function 2. The Hadamard Ansatz 3. The non-Hadamard behavior B. Proof of well defined foliation C. Useful integrals to define ζ D. The SSC Formalism and the Sudden Collapse of the quantum state References I. INTRODUCTION The surprising discovery of black hole radiation by S. Hawking [3] in the 1970's, has had an enormous influence in our ideas concerning the interface of quantum theory and gravitation. For instance, it has changed our perception regarding the laws of black hole thermodynamics, which, before that discovery, could have been regarded as mere analogies to our current view that they represent simply the ordinary thermodynamical laws, as they apply to situations involving black holes (see for instance[51]). This, in turn, has led to the quest to understand, on statistical mechanical terms, and within different proposals for a theory of quantum gravity, the area of the black hole horizon as a measure of the black hole entropy. In fact, the most popular programs in this regard, String Theory and Loop Quantum Gravity, have important success in this front. Furthermore, the fact that as the black hole radiates it must lose mass leads to some tension between the picture that emerges from the gravitational side and the basic tenants of quantum theory. This tension was first pointed out by Hawking [4] and has even been described by many theorists as the "Black Hole Information Paradox" (BHIP). The root of the tension is that, according to the picture that emerges from the gravitational side, it seems that one can start with a pure initial quantum state characterizing the system at some initial stage, which then evolves into something that, at the quantum level, can only be characterized as a highly mixed quantum state, while, the standard quantum mechanical considerations would lead one to expect a fully unitary evolution. There is even some debate as to whether or not this issue should be considered as paradoxical.