Nagoya University
Theoretical Elementary Particle Physics Laboratory

Date&Time Mon Jul 11 2022 (11:00 - 12:00)
Speaker
Shinji Mukohyama
Affiliation YITP
Title On the assumptions leading to the information loss paradox
Abstract 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 incompatibilitybetween (i) the validity of the laws of general relativity to describe infalling matter far from the Planckian regime, and (ii) the so-calledcentral dogma which states that as seen from an outside observer a black hole behaves like a quantum system whose number of degrees offreedom is proportional to the horizon area. We critically revise the standard arguments in support of the central dogma, and argue thatthey cannot hold true unless some new physics is invoked even before reaching Planck scales. This suggests that the information lossproblem, 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 holeevaporation where, instead, a consistent theory of quantum gravity is needed to make any prediction.
Remarks
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