The fuzzball proposal for black holes

TL;DR

The fuzzball proposal suggests black hole microstates are horizon-free solutions that replicate black holes asymptotically, potentially resolving issues like information loss, with current evidence mainly from AdS/CFT methods supporting this view.

Contribution

This review consolidates evidence for the fuzzball proposal, especially in D1-D5 systems, and discusses new derivations and future directions beyond supergravity approximations.

Findings

Support for fuzzball microstates from AdS/CFT

New derivations for D1-D5 black holes

Potential resolution of black hole information paradox

Abstract

The fuzzball proposal states that associated with a black hole of entropy S there are exp S horizon-free non-singular solutions that asymptotically look like the black hole but generically differ from the black hole up to the horizon scale. These solutions, the fuzzballs, are considered to be the black hole microstates while the original black hole represents the average description of the system. The purpose of this report is to review current evidence for the fuzzball proposal, emphasizing the use of AdS/CFT methods in developing and testing the proposal. In particular, we discuss the status of the proposal for 2 and 3 charge black holes in the D1-D5 system, presenting new derivations and streamlining the discussion of their properties. Results to date support the fuzzball proposal but further progress is likely to require going beyond the supergravity approximation and sharpening the definition of a "stringy fuzzball". We outline how the fuzzball proposal could resolve longstanding issues in black hole physics, such as Hawking radiation and information loss. Our emphasis throughout is on connecting different developments and identifying open problems and directions for future research.