News from Critical Collapse: Bondi Mass, Tails and Quasinormal Modes

TL;DR

This paper investigates critical gravitational collapse using Bondi coordinates and a massless scalar field, revealing connections between radiation signals, quasinormal modes, and the global structure of spacetime.

Contribution

It introduces a novel approach to studying critical collapse with Bondi coordinates, linking radiation features to black hole quasinormal modes and exploring null infinity's role.

Findings

Radiation at null infinity exhibits DSS behavior.

Period of radiation relates to black hole quasinormal modes.

Insights into global versus local aspects of critical collapse.

Abstract

We discuss critical gravitational collapse on the threshold of apparent horizon formation as a model both for the discussion of global aspects of critical collapse and for numerical studies in a compactified context. For our matter model we choose a self-gravitating massless scalar field in spherical symmetry, which has been studied extensively in the critical collapse literature. Our evolution system is based on Bondi coordinates, the mass function is used as an evolution variable to ensure regularity at null infinity. We compute radiation quantities like the Bondi mass and news function and find that they reflect the DSS behavior. Surprisingly, the period of radiation at null infinity is related to the formal result for the leading quasi-normal mode of a black hole with rapidly decreasing mass. Furthermore, our investigations shed some light on global versus local issues in critical collapse, and the validity and usefulness of the concept of null infinity when predicting detector signals.