Black shells and naked shells

TL;DR

This paper investigates the horizon dynamics during the collapse of thin dust shells, identifying critical surfaces and quasi-local horizons, and introduces the concept of naked shells that avoid horizon formation.

Contribution

It provides a detailed analysis of horizon behavior in dust shell collapse and introduces the notion of naked shells that circumvent horizon formation.

Findings

Existence of marginally outer trapped surfaces linked to quasi-local horizons

Identification of critical surfaces where coordinates interchange roles

Discovery of shell configurations that avoid horizon formation

Abstract

We study the collapse of a thin dust shell from the point of view of the horizon dynamics. We identify the critical surfaces at which time and space coordinates interchange their roles and investigate their properties by using the formalism of trapped surfaces. We show the existence of marginally outer trapped surfaces that are associated with the presence of quasi-local horizons. A particular shell configuration that avoids the formation of horizons is interpreted as naked shell.