Black Hole Remnants and the Information Loss Paradox

TL;DR

This paper reviews the concept of black hole remnants as a potential solution to the information loss paradox and firewall controversy, emphasizing their possible role in preserving unitarity and addressing singularity issues.

Contribution

It provides a comprehensive review of black hole remnants, discusses their challenges, and offers new insights into their role in resolving the information paradox and firewall controversy.

Findings

Remnants could serve as cosmic censors preventing singularities.

Black hole remnants may help resolve the information loss paradox.

Large interior geometry in remnants could mitigate firewall issues.

Abstract

Forty years after the discovery of Hawking radiation, its exact nature remains elusive. If Hawking radiation does not carry any information out from the ever shrinking black hole, it seems that unitarity is violated once the black hole completely evaporates. On the other hand, attempts to recover information via quantum entanglement lead to the firewall controversy. Amid the confusions, the possibility that black hole evaporation stops with a "remnant" has remained unpopular and is often dismissed due to some "undesired properties" of such an object. Nevertheless, as in any scientific debate, the pros and cons of any proposal must be carefully scrutinized. We fill in the void of the literature by providing a timely review of various types of black hole remnants, and provide some new thoughts regarding the challenges that black hole remnants face in the context of the information loss paradox and its latest incarnation, namely the firewall controversy. The importance of understanding the role of curvature singularity is also emphasized, after all there remains a possibility that the singularity cannot be cured even by quantum gravity. In this context a black hole remnant conveniently serves as a cosmic censor. We conclude that a remnant remains a possible end state of Hawking evaporation, and if it contains large interior geometry, may help to ameliorate the information loss paradox and the firewall controversy. We hope that this will raise some interests in the community to investigate remnants more critically but also more thoroughly.