Critical phenomena in gravitational collapse

TL;DR

This paper reviews the discovery and understanding of critical phenomena in gravitational collapse, highlighting their universal features, self-similarity, and significance for cosmic censorship and quantum gravity.

Contribution

It explains the existence of attractor solutions causing critical phenomena and discusses their implications for fundamental questions in general relativity and astrophysics.

Findings

Universality and scale invariance in black hole formation

Existence of self-similar solutions as attractors

Relevance to cosmic censorship and quantum gravity

Abstract

As first discovered by Choptuik, the black hole threshold in the space of initial data for general relativity shows both surprising structure and surprising simplicity. Universality, power-law scaling of the black hole mass, and scale echoing have given rise to the term "critical phenomena". They are explained by the existence of exact solutions which are attractors within the black hole threshold, that is, attractors of codimension one in phase space, and which are typically self-similar. Critical phenomena give a natural route from smooth initial data to arbitrarily large curvatures visible from infinity, and are therefore likely to be relevant for cosmic censorship, quantum gravity, astrophysics, and our general understanding of the dynamics of general relativity.