Information Paradox Research Articles

A BRIEF INTRODUCTION TO THE PHILOSOPHY OF INFORMATION

The term “information” and its various meanings across several domains have spawned a growing research area in the discipline of philosophy known as the philosophy of information (PI). The following briefly outlines a taxonomy of the field addressing: 1) what is the philosophy of information; 2) what is information; 3) open problems in the philosophy of information; 4) paradoxes of information; 5) philosophy as the philosophy of information; 6) information metaphysics; and 7) information ethics.

The tune of love and the nature(ness) of spacetime

The black hole information paradox is among the most outstanding puzzles in physics. I argue here there is yet another black hole quandary which, in light of the recent direct detection of gravitational waves by Advanced LIGO, reveals a new window to probe the nature of spacetime in the forthcoming era of ‘precision gravity.'

Grover Search and the No-Signaling Principle.

Two of the key properties of quantum physics are the no-signaling principle and the Grover search lower bound. That is, despite admitting stronger-than-classical correlations, quantum mechanics does not imply superluminal signaling, and despite a form of exponential parallelism, quantum mechanics does not imply polynomial-time brute force solution of NP-complete problems. Here, we investigate the degree to which these two properties are connected. We examine four classes of deviations from quantum mechanics, for which we draw inspiration from the literature on the black hole information paradox. We show that in these models, the physical resources required to send a superluminal signal scale polynomially with the resources needed to speed up Grover's algorithm. Hence the no-signaling principle is equivalent to the inability to solve NP-hard problems efficiently by brute force within the classes of theories analyzed.

Information retrieval from black holes

It is generally believed that, when matter collapses to form a black hole, the complete information about the initial state of the matter cannot be retrieved by future asymptotic observers, through local measurements. This is contrary to the expectation from a unitary evolution in quantum theory and leads to (a version of) the black hole information paradox. Classically, nothing else, apart from mass, charge and angular momentum is expected to be revealed to such asymptotic observers after the formation of a black hole. Semi-classically, black holes evaporate after their formation through the Hawking radiation. The dominant part of the radiation is expected to be thermal and hence one cannot know anything about the initial data from the resultant radiation. However, there can be sources of distortions which make the radiation non-thermal. Although the distortions are not strong enough to make the evolution unitary, these distortions carry some part of information regarding the in-state. In this work, we show how one can decipher the information about the in-state of the field from these distortions. We show that the distortions of a particular kind --- which we call {\it non-vacuum distortions} --- can be used to \emph{fully} reconstruct the initial data. The asymptotic observer can do this operationally by measuring certain well-defined observables of the quantum field at late times. We demonstrate that a general class of in-states encode all their information content in the correlation of late time out-going modes. Further, using a $1+1$ dimensional CGHS model to accommodate back-reaction self-consistently, we show that observers can also infer and track the information content about the initial data, during the course of evaporation, unambiguously. Implications of such information extraction are discussed.

Black holes as random particles: entanglement dynamics in infinite range and matrix models

We first propose and study a quantum toy model of black hole dynamics. The model is unitary, displays quantum thermalization, and the Hamiltonian couples every oscillator with every other, a feature intended to emulate the color sector physics of large-$\mathcal{N}$ matrix models. Considering out of equilibrium initial states, we analytically compute the time evolution of every correlator of the theory and of the entanglement entropies, allowing a proper discussion of global thermalization/scrambling of information through the entire system. Microscopic non-locality causes factorization of reduced density matrices, and entanglement just depends on the time evolution of occupation densities. In the second part of the article, we show how the gained intuition extends to large-$\mathcal{N}$ matrix models, where we provide a gauge invariant entanglement entropy for `generalized free fields', again depending solely on the quasinormal frequencies. The results challenge the fast scrambling conjecture and point to a natural scenario for the emergence of the so-called brick wall or stretched horizon. Finally, peculiarities of these models in regards to the thermodynamic limit and the information paradox are highlighted.

Quantum Gravity as Higher Dimensional Perspective

Although highly predictive in their respective macroscopic and microscopic domains of applicability, General Relativity and quantum mechanics are mathematically incompatible, perhaps most markedly in assumptions in their formalisms concerning the nature of space and time. In <em>perspective</em> we already have a conceptual structure that links the local, macroscopic frame and the remote, apparently microscopic frame. A mathematical principle is invoked as a natural limit on D(n), so that effects which are clearly perspectival at D=3 become ‘more real’ (<em>effectively</em> observer-independent) with each D(n) increment. For instance, the apparently microscopic becomes the effectively microscopic and <em>scale extremes are juxtaposed</em>, so that black holes are local, macroscopic vanishing-points, in a similar way to that in which in projective geometry the point at infinity is incorporated into the foreground. (In other words, <em>a black hole is a blown-up ‘Planck-scale’ singularity</em>.) Characteristics of the earthbound frame are applied to D>3, suggesting a physical basis for entanglement, and perspectival interpretations of quantum gravity, dimensional reduction and the information paradox. We claim that the familiar processes whereby multiple physical states become describable by a single state in which composition information appears to be lost (e.g., ‘falling into a black hole’, the state of quantum linearity, and the state of freefall) are all examples of effective convergence of a space or <em>n</em>-surface to a single point of perspective.

Black holes, information, and the universal coefficient theorem

General relativity is based on the diffeomorphism covariant formulation of the laws of physics while quantum mechanics is based on the principle of unitary evolution. In this article, I provide a possible answer to the black hole information paradox by means of homological algebra and pairings generated by the universal coefficient theorem. The unitarity of processes involving black holes is restored by the demanding invariance of the laws of physics to the change of coefficient structures in cohomology.

Collapsing objects with the same gravitational trajectory can radiate away different amount of energy

We study radiation emitted during the gravitational collapse from two different types of shells. We assume that one shell is made of dark matter and is completely transparent to the test scalar (for simplicity) field which belongs to the standard model, while the other shell is made of the standard model particles and is totally reflecting to the scalar field. These two shells have exactly the same mass, charge and angular momentum (though we set the charge and angular momentum to zero), and therefore follow the same geodesic trajectory. However, we demonstrate that they radiate away different amount of energy during the collapse. This difference can in principle be used by an asymptotic observer to reconstruct the physical properties of the initial collapsing object other than mass, charge and angular momentum. This result has implications for the information paradox and expands the list of the type of information which can be released from a collapsing object.

Conformal blocks beyond the semi-classical limit

c. We compute Virasoro blocks in the heavy-light, large c limit, extending our previous results by determining perturbative 1=c corrections. We obtain explicit closed-form expressions for both the ‘semi-classical’ h 2 =c 2 and ‘quantum’ hL=c 2 corrections to the vacuum block, and we provide integral formulas for general Virasoro blocks. We comment on the interpretation of our results for thermodynamics, discussing how monodromies in Euclidean time can arise from AdS calculations using ‘geodesic Witten diagrams’. We expect that only non-perturbative corrections in 1=c can resolve the singularities associated with the information paradox.

Remarks on the necessity and implications of state-dependence in the black hole interior

We revisit the "state-dependence" of the map that we proposed recently between bulk operators in the interior of a large AdS black hole and operators in the boundary CFT. By refining recent versions of the information paradox, we show that this feature is necessary for the CFT to successfully describe local physics behind the horizon --- not only for single-sided black holes but even in the eternal black hole. We show that state-dependence is invisible to an infalling observer who cannot differentiate these operators from those of ordinary quantum effective field theory. Therefore the infalling observer does not observe any violations of quantum mechanics. We successfully resolve a large class of potential ambiguities in our construction. We analyze states where the CFT is entangled with another system and show that the ER=EPR conjecture emerges from our construction in a natural and precise form. We comment on the possible semi-classical origins of state-dependence.

Quantum corrections to the thermodynamics of Schwarzschild–Tangherlini black hole and the generalized uncertainty principle

We investigate the thermodynamics of Schwarzschild-Tangherlini black hole in the context of the generalized uncertainty principle. The corrections to the Hawking temperature, entropy and the heat capacity are obtained via the modified Hamilton-Jacobi equation. These modifications show that the GUP changes the evolution of Schwarzschild-Tangherlini black hole. Specially, the GUP effect becomes susceptible when the radius or mass of black hole approach to the order of Planck scale, it stops radiating and leads to black hole remnant. Meanwhile, the Planck scale remnant can be confirmed through the analysis of the heat capacity. Those phenomenons imply that the GUP may give a way to solve the information paradox. Besides, we also investigate the possibilities to observe the black hole at LHC, the results demonstrate that the black hole can not be produced in the recent LHC.

One-Shot Decoupling and Page Curves from a Dynamical Model for Black Hole Evaporation.

One-shot decoupling is a powerful primitive in quantum information theory and was hypothesized to play a role in the black hole information paradox. We study black hole dynamics modeled by a trilinear Hamiltonian whose semiclassical limit gives rise to Hawking radiation. An explicit numerical calculation of the discretized path integral of the S matrix shows that decoupling is exact in the continuous limit, implying that quantum information is perfectly transferred from the black hole to radiation. A striking consequence of decoupling is the emergence of an output radiation entropy profile that follows Page's prediction. We argue that information transfer and the emergence of Page curves is a robust feature of any multilinear interaction Hamiltonian with a bounded spectrum.

Super-massive objects in Yarman–Arik–Kholmetskii (YARK) gravitation theory

We continue to analyze the implications of the gravitational framework of our theoretical approach, christened YARK (abbreviated from Yarman–Arik–Kholmetskii), with respect to super-massive celestial bodies. We emphasize in particular that a gravitating test particle in the presence of a ponderable mass must adhere to the law of energy conservation, which remarkably does not yield any singularity according to YARK. Even so, for a given spherically shaped extremely compact super-massive body, one can achieve a theoretical radius below which “light” of, say, the visible frequency range can indeed be trapped. Yet, such a radius comes out to be tens of times shorter than the threshold radius for black hole formation as established by the general theory of relativity (GTR). In accordance with our derivations, the minimal mass for a celestial object capable of recapturing emitted light in its environs — similar to textbook “intermediate class black holes” — is found to be about 103MS, where MS stands for the mass of the Sun. For less massive celestial objects, the crucial radius that produces a “YARK black hole” (i.e., without singularity) corresponds to a higher density than the density of a baryon; and hence, such entities cannot apparently exist in nature. Black holes allowed therefore in our approach are not related, in any case, to the singularity conceptualization of GTR. As a consequence, we are able to present a resolution to the “black hole information paradox”. The findings of YARK will be discussed hereinafter with regards to the foundations of observational cosmology.

The Holographic Universe

How is a black hole in a 5-D anti de Sitter space like a flat 4-D field of particles and radiation? Jean-Pierre Luminet explains the holographic principle, the Maldacena conjecture, and the resolution of the information paradox.

Extracting Information about the Initial State from the Black Hole Radiation.

The crux of the black hole information paradox is related to the fact that the complete information about the initial state of a quantum field in a collapsing spacetime is not available to future asymptotic observers, belying the expectations from a unitary quantum theory. We study the imprints of the initial quantum state contained in a specific class of distortions of the black hole radiation and identify the classes of in states that can be partially or fully reconstructed from the information contained within. Even for the general in state, we can uncover some specific information. These results suggest that a classical collapse scenario ignores this richness of information in the resulting spectrum and a consistent quantum treatment of the entire collapse process might allow us to retrieve much more information from the spectrum of the final radiation.

New study attempts to resolve black hole information paradox

New study attempts to resolve black hole information paradox

Why Geometry Radiates: Quantum Gravity as Perspective

It is reasonably expected 1) that a theory of quantum gravity will unify the extremes of scale currently described by General Relativity and quantum mechanics, and 2) that black holes are the crucible from which a theory of quantum gravity will emerge. In perspective, we already have a mechanism that links the local, macroscopic frame with the remote, apparently microscopic frame. A simple mathematical principle acts as a limit on D(n), suggesting a “maximum physical reality”, and that effects which are clearly perspectival at D=3 become “more real” (effectively observer-independent) with each D(n) increment. The model suggests alternative interpretations of gravitation and the quantum, entanglement, space, the Standard Model of particles and interactions, black holes, the measurement problem and the information paradox.

Non‐Thermal Corrections to Hawking Radiation Versus the Information Paradox**

We provide a model‐independent argument indicating that for a black hole of entropy N the non‐thermal deviations from Hawking radiation, per each emission time, are of order , as opposed to . This fact abolishes the standard a priory basis for the information paradox.

Information Paradox : Drowning in Information, Starving for Knowledge [Commentary

Examines the paradox of an world of increasing information availability and the qualit of information people are receiving and comprehending. Explores the impact to society as a whole.

Local Operators in the Eternal Black Hole.

In the AdS/CFT correspondence, states obtained by Hamiltonian evolution of the thermofield doubled state are also dual to an eternal black-hole geometry, which is glued to the boundary with a time shift generated by a large diffeomorphism. We describe gauge-invariant relational observables that probe the black hole interior in these states and constrain their properties using effective field theory. By adapting recent versions of the information paradox we show that these observables are necessarily described by state-dependent bulk-boundary maps, which we construct explicitly.