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The Quantum Structure of Black Holes and the Recovery of Information

Periodic Reporting for period 1 - QBH Structure (The Quantum Structure of Black Holes and the Recovery of Information)

Reporting period: 2019-01-01 to 2020-06-30

This project addresses a foundational issue about black holes and what happens to the matter that falls into them. Conventional combinations of general relativity and quantum mechanics lead to a fundamental conflict that is best characterized through the information paradox: Hawking showed that quantum black holes will ultimately radiate away all their mass, or evaporate, into largely featureless thermal radiation. This radiation is independent of how the black hole formed and so it is impossible to use it to reconstruct the initial state of the matter that made the black hole. Such a loss of information about the initial state is fundamentally incompatible with the precepts of quantum mechanics.

This project is using string theory, and higher dimensional theories of gravity, to reveal the quantum properties of black holes through the construction and analysis of “microstate geometries.” This research focusses on the dynamics of matter falling into such geometries and determines they extent to which they replicate the observed properties of black holes without producing an information paradox. This work involves computing how matter is reprocessed through microstate geometries and how such geometries describe the microstructure that must emerge at the event horizons of black holes. By exploring the similarities and differences in the predictions coming from black holes and microstate geometries the project will explore potential macroscopic, measurable signatures of the horizon-scale microstructure.

Since quantum mechanics and general relativity are essential to the technological functioning of modern society (through things like microprocessors and global positioning systems), it is essential to resolve conflicts between these two extremely important theories of Nature. By resolving the conflict, we will also learn much about behaviour of black holes, the quantum properties of matter near black holes, and perhaps even the quantum structure of space and time.
The project has progressed extremely well, resulting in 18 publications: of which 7 have already appeared in refereed journals, another 9 are yet to be submitted and two are reports, or lecture notes.

We have also organized and held two Conferences/Workshops that led to new and deeper insights:

Black-Hole Microstructure Workshop – May 27-31, 2019
Black-Hole Microstructure Conference - June 8-12, 2020 (23 speakers, 285 participants)

In addition, Warner, Bena and Minasian have given a total of 20 plenary conference talks. Bena and Warner attended, and gave talks at two meetings, with members of the LIGO collaboration. The goal was to start a dialogue about possible observable signatures of microstate structure. This objective has been further advanced in several publications.

There have been substantial advances on the several of the primary objectives in the original proposal. Highlights include:

1) The construction of by far the largest, most general class of supersymmetric microstate geometries ever achieved and the matching of these geometries to precise microstructure of black hole states.
2) Establishing how microstate geometries replicate black hole behavior without information loss: how infalling matter undergoes thermal decay and is incorporated, or “scrambled,” into microstate geometries; how trapped matter can tunnel out of microstate geometries.
3) A huge reduction in the complexity of the construction of new families of far more generic, non-supersymmetric microstate geometries. Prior to my team’s work in the last few months, it seemed that the construction of such generic microstate geometries was out of reach of even the most advanced numerical algorithms and supercomputers. Our most recent work has brought this important goal within reach, and in the next phase of the project we anticipate using our newly developed techniques to achieve other major objectives of the proposal.
4) Finding and computing new, potentially-measurable signatures, or multipole moments, that characterize different classes of horizon-scale black-hole microstructure.
This is partially covered by the highlights above, and particularly by the advances we have made towards the construction of far more generic, non-supersymmetric microstate geometries.

In the next phase of the project we anticipate

1) The construction of the first non-trivial, non-supersymmetric microstate geometries corresponding to black holes. These are expected to exhibit many of the features of Hawking radiation from black holes but without an information paradox.
2) A much more detailed analysis of the scrambling and trapping of matter in microstate geometries and its re-radiation out as some form of Hawking radiation.
3) Additional progress on the other objectives of the original proposal, especially on new horizon-scale physics