Global symmetry, Euclidean gravity, and the black hole information problem

We consider the capacity of entanglement in models related with the gravitational phase transitions. The capacity is labeled by the replica parameter which plays a similar role to the inverse temperature in thermodynamics. In the end of the world brane model of a radiating black hole the capacity has a peak around the Page time indicating the phase transition between replica wormhole geometries of different types of topology. Similarly, in a moving mirror model describing Hawking radiation the capacity typically shows a discontinuity when the dominant saddle switches between two phases, which can be seen as a formation of island regions. In either case we find the capacity can be an invaluable diagnostic for a black hole evaporation process.

mentioning

confidence: 99%

Probing Hawking radiation through capacity of entanglement

Kawabata

Nishioka

Okuyama

et al. 2021

“…Another prominent example is the swampland program in string theory that aims at delineating the boundary between theories that could arise from a string theory and those that could not, see [26] for a review. Within this context, arguments against the existence of global continuous symmetries exist [27][28][29][30] and have been substantiated to some degree [31][32][33] in AdS/CFT. In their simplest form, these arguments rely on the incompatibility of the conservation of a global charge and a complete Hawking evaporation of black-hole solutions that would follow by an extension of semi-classical arguments into the quantum-gravity regime.…”

Section: Jhep05(2021)036mentioning

confidence: 99%

Constraints on discrete global symmetries in quantum gravity

Ali

Eichhorn

Pauly

et al. 2021

The question whether global symmetries can be realized in quantum-gravity-matter-systems has far-reaching phenomenological consequences. Here, we collect evidence that within an asymptotically safe context, discrete global symmetries of the form ℤn, n > 4, cannot be realized in a near-perturbative regime. In contrast, an effective-field-theory approach to quantum gravity might feature such symmetries, providing a mechanism to generate mass hierarchies in the infrared without the need for additional fine-tuning.

“…The computation of the von Neumann entropy of the radiation was obtained by using the Ryu-Takayanagi formula [18] that can be derived from the gravitational path integral under the assumption of holography [33,52]. As a result the Page curve was reproduced, and several authors [11][12][13][14][15] claimed that the entropy problem (paradox) was solved.…”

Section: Jhep10(2021)081mentioning

confidence: 99%

“…[54] where it was claimed that the transfer of information based on the island computation requires a nonlocal interaction term in the Hamiltonian. On the other hand, it is also worth mentioning that other authors [52] claim that holography must be imposed even when performing the standard Euclidean computation [55] of the Gibbons-Hawking entropy, or in other words that the Euclidean gravitational path integral is only valid for holographic theories.…”

Section: Jhep10(2021)081mentioning

confidence: 99%

On the assumptions leading to the information loss paradox

Buoninfante

Filippo

Mukohyama

2021

The information loss paradox is usually stated as an incompatibility between general relativity and quantum mechanics. However, the assumptions leading to the problem are often overlooked and, in fact, a careful inspection of the main hypothesises suggests a radical reformulation of the problem. Indeed, we present a thought experiment involving a black hole that emits radiation and, independently of the nature of the radiation, we show the existence of an incompatibility between (i) the validity of the laws of general relativity to describe infalling matter far from the Planckian regime, and (ii) the so-called central dogma which states that as seen from an outside observer a black hole behaves like a quantum system whose number of degrees of freedom is proportional to the horizon area. We critically revise the standard arguments in support of the central dogma, and argue that they cannot hold true unless some new physics is invoked even before reaching Planck scales. This suggests that the information loss problem, in its current formulation, is not necessarily related to any loss of information or lack of unitarity. Therefore, in principle, semiclassical general relativity and quantum mechanics can be perfectly compatible before reaching the final stage of the black hole evaporation where, instead, a consistent theory of quantum gravity is needed to make any prediction.