The fuzzball proposal for black holes

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.

Non-BPS multi-bubble microstate geometries

“…Setting n = 0 we find for the JMaRT solution M 1 the sequence 8) implying that H 3 (M 1 ) = Z and H 2 (M 1 ) is trivial, so one indeed finds that M 1 ∼ = R 2 × S 3 , and we recover the nontrivial three-cycle of the JMaRT solution.…”

“…Similarly, the vector fields w 0 and w 3 which appear in the metric are determined from the first-order equations: 8) while the vector field, ω, corresponding to the time fibration, is determined by…”

“…Over the past few years, following its sharpening using quantum information theory [2], it has become increasingly clear that in order to solve this paradox there must be new physics at the black hole horizon. There are many arguments that lead to the same conclusion, some focused on the experience of infalling observers [3][4][5][6] (see also [7]), some based on the AdS-CFT correspondence [8,9], and some based on quantizing fields at the horizon [10].…”

An infalling observer in AdS/CFT

“…Indeed, this is the key issue in all the recent discussions on whether the nature of the horizon needs to be modified. For example, several regular solutions, with the same charges as the black hole, have been found in several theories (see [78] for a review and references to the very extended literature). These solutions are extremely interesting.…”

Doubly-fluctuating BPS solutions in six dimensions

“…construction of microstate geometries (see [2,3], and for reviews, see [4][5][6][7][8]). Secondly, sixdimensional supergravity underlies the study of AdS 3 ×S 3 holography (see, for example, [9][10][11][12][13]).…”