Snowmass White Paper: Micro- and Macro-Structure of Black Holes

Abstract

The black-hole information paradox provides a stringent test of would-be theories of quantum gravity. String theory has made significant progress toward a resolution of this paradox, and has led to the fuzzball and microstate geometry programs. The central thesis of these programs is that only string theory has sufficiently many degrees of freedom to resolve black-hole microstructure, and that horizons and singularities are artifacts of attempting to describe gravity using a theory that has too few degrees of freedom to resolve the physics. Fuzzballs and microstate geometries recast black holes within string theory as horizonless and singularity-free objects that not only resolve the paradox but provide new insight into the underlying microstructure. We give an overview of this approach, summarize its current status and describe future prospects and insights that are now within reach.

Fuzzballs and Microstate Geometries: Black-Hole Structure in String Theory

“…In Appendix A we compare and contrast the fuzzball program with some of the more recent popular approaches to the information problem, and in Appendix B we discuss an older confusion, the firewall, and how its only incarnation that makes any sense is some form of hot fuzzball. This paper is an expanded version of our Snowmass White Paper [1].…”

“…When one compresses matter into a state in which its entropy approaches 1 4 A, where A is its surface area in Planck units, then it becomes an intrinsically quantum object. That is, quantum effects become large at the horizon scale.…”

“…We summarize the current status of this approach and describe future prospects and additional insights that are now within reach. This paper is an expanded version of our Snowmass White Paper [1].…”

Snowmass White Paper: Implications of Quantum Gravity for Particle Physics

“…Although exploring the growing diversity of string theory "data" in search for underlying patterns may be a hopeful endeavor, it is hard to ignore that the earliest insight for the best-motivated conjectures, such as the absence of global symmetries or the holographic entropy bounds, actually originated from studying the properties of black holes. Exploring the properties of these fascinating objects under a diversity of circumstances in search for additional intuition has seen renewed interest in recent times; see, e.g., the recent review [53] and the Snowmass white papers [54][55][56]. Perhaps not coincidentally, recent progress on the black hole information puzzle forgoes input from perturbative string theory, relying instead on semiclassical gravity techniques [57,58], and renewing hopes that constraints such as the absence of global symmetries could be understood using similar techniques [9][10][11].…”

Schwarzschild-like Topological Solitons

“…Smooth gravitational solitons with interesting topology can exist in a variety of supergravity theories that descend from string theories. They are staples in the construction of explicit models for holography [1,2], and for microstate geometries in black hole physics [3][4][5]. More recently, their existence in generic theories of gravity have been demonstrated beyond the framework of supergravity and supersymmetry [6][7][8][9][10].…”