Showing papers on "Black hole information paradox published in 2023"

Resolving the Information Paradox with Probabilistic Spacetime

Abstract: It has been 50 years since Hawking described the black hole (BH) information paradox. The combination of BH radiation and subsequent BH evaporation was found to take trapped information into oblivion contrary to the law of conservation of quantum information. Numerous attempts have been made since to resolve this paradox. A brief review herein documents how all these attempts have significant shortcomings, meaning the paradox is still unresolved. A relatively new cosmological theory offers a resolution despite not being developed for that purpose. The theory, entitled the probabilistic spacetime theory (PST), starts with an alteration in one basic assumption compared to all current cosmological theories. Spacetime, instead of being seen as a void or container of other entities, is viewed as the most fundamental entity in the universe, composed of energy fragments, and (in keeping with the conservation principle) impermeable to destruction. The potential contribution of the PST in resolving the information paradox is delineated, with the finding that the single change in the conceptualization of spacetime results in the disappearance of the paradox and not information.

How an exact discrete symmetry can preserve black hole information or Turning a black hole inside out

Abstract: To apply the laws of General Relativity to quantum black holes, one first needs to remove the horizon singularity by means of Kruskal-Szekeres coordinates. This however doubles spacetime, which thereby is equipped with an exact binary symmetry. All particles near a black hole share the same symmetry, and conservation of this symmetry may completely remove the information paradox: the quantum black hole has no interior, or equivalently, the black hole interior is a quantum clone of the exterior region. These observations, totally overlooked in most of the literature on quantum black holes, resolve some issues concerning conservation of information. Some other problems do remain.

On quantum information before the Page time

Abstract: While recent progress in the black hole information problem has shown that the entropy of Hawking radiation follows a unitary Page curve, the quantum state of Hawking radiation prior the Page time is still treated as purely thermal, containing no information about the microstructure of the black hole. We demonstrate that there is significant quantum information regarding the quantum state of the black hole in the Hawking radiation prior to the Page time. By computing of the quantum fidelity in a 2D boundary conformal field theory (BCFT) model of black hole evaporation, we demonstrate that an observer outside of an evaporating black hole may distinguish different black holes via measurements of the Hawking radiation at \textit{any} time during the evaporation process, albeit with an exponentially large number of measurements. Furthermore, our results are universal, applicable to general BCFTs including those with large central charge and rational BCFTs. The techniques we develop for computing the fidelity are more generally applicable to excited states in CFT. As such, we are able to characterize more general aspects of thermalization in 2D conformal field theory.

Black hole information recovery in JT gravity

Abstract: A bstract We consider the issue of information recovery for an object carrying energy and entropy into a black hole using the generalized entropy formalism, in the context of JT gravity where the backreaction problem can be solved exactly. We verify the main aspects of the Hayden-Preskill scenario but with some refinements. We show that the information is encoded in the Hawking radiation in a redundant way, as expected for a quantum error correcting code. We show how quantum extremal surfaces associated to information recovery have the form of a python’s lunch and thereby show that the complexity of decoding is exponential in a combination of the entropy shift of the black hole and the entropy of the object. We also show that an infalling observer must have a smooth experience at the horizon and we calculate their endurance proper time inside the black hole before they are radiated out.

On the Resilience of Black Hole Evaporation: Gravitational Tunneling through Universal Horizons

Abstract: Using a quantum tunneling derivation, we show the resilience of Hawking radiation in Lorentz violating gravity. In particular, we show that the standard derivation of the Hawking effect in relativistic quantum field theory can be extended to Lorentz breaking situations thanks to the presence of universal horizons (causal boundaries for infinite speed signals) inside black hole solutions. Correcting previous studies, we find that such boundaries are characterized by a universal temperature governed by their surface gravity. We also show that within the tunneling framework, given the pole structure and the tunneling path, only a vacuum state set in the preferred frame provides a consistent picture. Our results strongly suggest that the robustness of black hole thermodynamics is ultimately linked to the consistency of quantum field theories across causal boundaries.

How an exact discrete symmetry can preserve black hole information or Turning a black hole inside out

Abstract: To apply the laws of General Relativity to quantum black holes, one first needs to remove the horizon singularity by means of Kruskal-Szekeres coordinates. This however doubles spacetime, which thereby is equipped with an exact binary symmetry. All particles near a black hole share the same symmetry, and conservation of this symmetry may completely remove the information paradox: the quantum black hole has no interior, or equivalently, the black hole interior is a quantum clone of the exterior region. These observations, totally overlooked in most of the literature on quantum black holes, resolve some issues concerning conservation of information. Some other problems do remain.

On the Resilience of Black Hole Evaporation: Gravitational Tunneling through Universal Horizons

Abstract: Using a quantum tunneling derivation, we show the resilience of Hawking radiation in Lorentz violating gravity. In particular, we show that the standard derivation of the Hawking effect in relativistic quantum field theory can be extended to Lorentz breaking situations thanks to the presence of universal horizons (causal boundaries for infinite speed signals) inside black hole solutions. Correcting previous studies, we find that such boundaries are characterized by a universal temperature governed by their surface gravity. We also show that within the tunneling framework, given the pole structure and the tunneling path, only a vacuum state set in the preferred frame provides a consistent picture. Our results strongly suggest that the robustness of black hole thermodynamics is ultimately linked to the consistency of quantum field theories across causal boundaries.

Quantum strong cosmic censorship and black hole evaporation

Abstract: It is common folklore that semiclassical gravity suggests that, in the process of black hole formation and subsequent evaporation by Hawking radiation, an initially pure state can evolve into a mixed state. This is known as the \emph{information loss puzzle} (or {\it paradox}). Here, we argue that a quantum version of strong cosmic censorship, for which we give a conjectural statement and has strong supporting evidence, indicates that the semiclassical description of the evaporation process breaks down at the final evaporation stage. We argue further that, if taken at face value, semiclassical gravity predicts the development of a future singularity instead of a post-evaporation region where quantum (and classical) predictability breaks down and where information is lost. We thus argue that there are no reasons to expect a failure of unitarity or predictability for any quantum gravity theory that can `cure' spacetime singularities, as this is not even suggested by semiclassical arguments.

Three way information paradox and its resolution using islands

Abstract: Black holes possess finite degrees of freedom and thus cannot fuel unbounded entanglement growth of any system. Instead of the usual information paradox where the coupled system is one entity, the Hawking radiation, here we couple a black hole $\chi_0$ with two infinite entities: a thermal bath $\chi_1$ and an auxiliary system $\chi _2$. This produces a novel information paradox in the sense that gravitational correction to black hole entropy does not rule out paradoxical growth of $\chi _1$ and $\chi _2$ entropies. This immediately raises what kind of resolution such a paradox has, and we address this question working in the AdS$_2$ JT gravity model, using the island formula, and ideas of entanglement monogamy. We find the quantum extremal surface that cures the black hole entropy growth, argue to the nature of how $\chi _1$ and $\chi _2$ entropies must behave using monogamy, and derive an island which satisfies these expectations. A direct consequence of our results is that gravitation builds entanglement between $\chi _1$ and $\chi _2$, even though they start out independently.

On information paradox and the fate of black holes

Abstract: A sketchy review of the "island" paradigm in black hole evaporation theory, which actually brings us back to the old idea that interior of black hole decouples from our universe after Page time, so that Hawking radiation is entangled with emerging new universe, thus leaving no room for the information paradox. Instead this provides a self-consistent description of multiverse, where every black hole in a parent universe is a white hole -- the origin -- of a new one.

Hawking Radiation from the Boundary Scalar Field and the Information Loss Paradox

Abstract: Hawking radiation is an essential property of the quantum black hole. It results in the information loss paradox and provides an important clue with regard to the unification of quantum mechanics and general relativity. In previous work, the boundary scalar fields on the horizon of black holes were used to determine the microstates of BTZ black holes and Kerr black holes. They account for Bekenstein–Hawking entropy. In this paper, we show that the Hawking radiation can also be derived from those scalar fields. Hawking radiation is a mixture of the thermal radiation of right- and left-moving sectors at different temperatures. Based on this result, for static BTZ black holes and Schwarzschild black holes, we propose a simple solution for the information loss paradox; i.e., the Hawking radiation is pure due to its entanglement between the left-moving sector and the right-moving sector. This entanglement may be detected in an analogue black hole in the near future.

Turing Machines Behind the Horizon: Modeling Black Hole Interiors as Transfinite Limited Turing Machines

Abstract: The information encoded in the Hawking radiation emitted from an evaporating black hole has puzzled astrophysicists and computer scientists alike for decades. Recent developments in quantum complexity theory and post-quantum cryptography shed light on a family of radical approaches to treat black hole interiors as systems beyond thermal states with high energy and density. In this paper, this study attempts to model the interior of a black hole using weaker variants of Infinite Time Turing Machines. This study curates two separate models—first based on the entanglement entropy of the evaporating black hole following the Page curve and the other based on the EBH quantum states of the same. This approach also highlights how the choice of the limit state significantly impacts the treatment of black hole interior encoding. Finally, the study shows how our model follows the Page curve and the entanglement wedge casually as a consequence of the correct choice of transition function. The contribution of our paper is to highlight the utility of classical computational models to generalize over high-energy thermal states like black holes.

The holographic map of an evaporating black hole

Abstract: A bstract We construct a holographic map that takes the semi-classical state of an evaporating black hole and its Hawking radiation to a microscopic model that reflects the scrambling dynamics of the black hole. The microscopic model is given by a nested sequence of random unitaries, each one implementing a scrambling time step of the black hole evolution. Differently from other models, energy conservation and the thermal nature of the Hawking radiation are taken into account. We show that the QES formula follows for the entropy of multiple subsets of the radiation and black hole. We further show that a version of entanglement wedge reconstruction can be proved by computing suitable trace norms and quantum fidelities involving the action of a unitary on a subset of Hawking partners. If the Hawking partner is in an island, its unitary can be reconstructed by a unitary on the radiation. We also adopt a similar setup and analyse reconstruction of unitaries acting on an infalling system.

On the irrelevance of the scrambling power of gravity for black hole radiation

Abstract: Black holes are a recently observed theoretical prediction of General Relativity, characterized by event horizons, from which information cannot escape. Examined through the lenses of quantum mechanics, they can radiate at a definite temperature inverse to their mass and horizon radius. Hawking radiation, whose spectrum was calculated considering particles scattering off black holes, is connected to the paradox of the loss of information falling into them. Information can become non-fungible, due to scrambling. We demonstrate this feature not to be restricted to curved space-times: soft radiation scattering in a flat space-time does scramble information as well. To this end, we compute the scrambling of information through the tripartite mutual information in a scattering process off a black hole and compare it with the flat space-time analog. We show that the scrambling power of the gravitational field of a black hole is negligible with respect to the scrambling power of flat space-time.

Holography and the Page curve of an evaporating black hole

Abstract: We consider a radiating black hole with a holographic dual such that its entanglement entropy does not exceed the Bekenstein-Hawking entropy, to obtain a Page curve. We make use of some mathematical identities that should be held for the entanglement entropy to be well-defined. This work is not going to give a resolution to the information paradox. Rather it shows that the general shape of the Page curve is a consequence of holography, independent of the details of gravitation theory.

entropy of the entangled Hawking radiation

Abstract: Entropic information theory, as a unified informational theory, presents a new informational theoretical framework capable of fully describing the evaporation of the black holes phenomenon while resolving the information paradox, reconciling quantum formalism and relativistic formalism in a single approach. With a set of five new equivalent equations expressing entropy, and by introducing the Hawking temperature into one of them, it is possible to solve the black holes information paradox by being able to calculate the entropy of entangled Hawking radiation, entangled with the fields inside black holes, allowing us to extract information from inside black holes. The proposed model solves the information paradox of black holes by calculating a new entropy formula for the entropy of black holes as equal to the entropy of the pure state of entangled Hawking radiation, itself equal to the fine-grained entropy or von Neumann entropy, itself according to the work of Casini and Bousso equal to the Bekenstein bound which is itself equal, being saturated by Bekenstein-Hawking entropy, at this same entropy. Moreover, since the law of the entropy horizon of black holes turns out to be a special case of the Ryu-Takayanagi conjecture, this general formula for the fine-grained entropy of quantum systems coupled to gravity, equalizes the entropy of entangled Hawking radiation with the gravitational fine-grained entropy of black holes, and makes it possible to relate this resolution of the information paradox of black holes based on the concept of mass of the information bit to quantum gravity explaining the emergence of the quantum gravity process through the fundamentality of entangled quantum information.

Stimulated Emission of Radiation and the Black Hole Information Problem

Abstract: The quantum theory of black holes has opened up a window to study the intersection of general relativity and quantum field theory, but perceived paradoxes concerning the fate of classical information directed at a black hole horizon, as well as concerning the unitarity of the evaporation process, have led researchers to question the very foundations of physics. In this pedagogical review I clarify the ramifications of the fact that black holes not only emit radiation spontaneously, but also respond to infalling matter and radiation by emitting approximate clones of those fields in a stimulated manner. I review early purely statistical arguments based on Einstein's treatment of black bodies, and then show that the Holevo capacity of the black hole (the capacity to transmit classical information through a quantum channel) is always positive. I then show how stimulated emission turns the black hole into an almost optimal quantum cloning machine, and furthermore discuss the capacity of black holes to transmit quantum information. Taking advantage of an analogy between black hole physics and non-linear optics I show that a calculation of the evolution of a black hole over time, using a discretization of the black hole $S$-matrix path integral, yields well-behaved Page curves suggesting that black hole evaporation is unitary. Finally, I speculate about possible observable consequences of stimulated emission of radiation in black holes.

The Holographic Map of an Evaporating Black Hole

Abstract: We construct a holographic map that takes the semi-classical state of an evaporating black hole and its Hawking radiation to a microscopic model that reflects the scrambling dynamics of the black hole. The microscopic model is given by a nested sequence of random unitaries, each one implementing a scrambling time step of the black hole evolution. Differently from other models, energy conservation and the thermal nature of the Hawking radiation are taken into account. We show that the QES formula follows for the entropy of multiple subsets of the radiation and black hole. We further show that a version of entanglement wedge reconstruction can be proved by computing suitable trace norms and quantum fidelities involving the action of a unitary on a subset of Hawking partners. If the Hawking partner is in an island, its unitary can be reconstructed by a unitary on the radiation and so the Hawking partners are not in any sense behind the horizon of the black hole. We also consider the problem of reconstruction for unitaries acting on an infalling system.

Black hole information paradox as an instance of the paradox of reversible processes

Abstract: It is noted that the black hole information paradox is an instance of the paradox of reversible processes, in case late-stage black hole states are approximated by thermodynamic equilibrium states, as conventionally expected. Some purported classical solutions to the paradox of reversible processes, such as the quasi-process interpretation, are shown to be insufficient in light of black holes. Three leading solutions to the information paradox - holography of information, replica wormholes and fuzzballs - are cast in the language of a reversible process, which then suggest different solutions to the paradox of reversible processes.