Critical phenomena at the threshold of black hole formation for collisionless matter in spherical symmetry

TL;DR

This paper investigates the critical behavior at the threshold of black hole formation in spherical, collisionless matter collapse using numerical simulations, revealing Type I critical phenomena with static unstable solutions.

Contribution

It provides the first detailed numerical analysis of critical phenomena in collisionless matter collapse, demonstrating Type I behavior and characterizing the critical solutions.

Findings

Critical behavior is Type I with finite-mass black holes.

Critical solutions are static and unstable with specific momentum distributions.

Lifetimes of near-critical configurations follow power-law scaling.

Abstract

We perform a numerical study of the critical regime at the threshold of black hole formation in the spherically symmetric, general relativistic collapse of collisionless matter. The coupled Einstein-Vlasov equations are solved using a particle-mesh method in which the evolution of the phase-space distribution function is approximated by a set of particles (or, more precisely, infinitesimally thin shells) moving along geodesics of the spacetime. Individual particles may have non-zero angular momenta, but spherical symmetry dictates that the total angular momentum of the matter distribution vanish. In accord with previous work by Rein et al, our results indicate that the critical behavior in this model is Type I; that is, the smallest black hole in each parametrized family has a finite mass. We present evidence that the critical solutions are characterized by unstable, static spacetimes, with non-trivial distributions of radial momenta for the particles. As expected for Type I solutions, we also find power-law scaling relations for the lifetimes of near-critical configurations as a function of parameter-space distance from criticality.