Quasi-black holes: general features and purely field configurations

TL;DR

Quasi-black holes are objects near horizon formation that do not collapse, and they can exist in purely field configurations like electromagnetic and scalar fields, with specific properties and exact solutions.

Contribution

This paper characterizes the general features of quasi-black holes and demonstrates their existence in field-only configurations without matter, providing explicit solutions.

Findings

QBH metrics have specific limiting behaviors as parameters tend to zero.

QBHs can exist in electromagnetic and scalar field configurations without matter.

Explicit exact solutions of QBHs are constructed and analyzed.

Abstract

Objects that are on the threshold of forming the horizon but never collapse are called quasi-black holes (QBHs). We discuss the properties of the general spherically symmetric QBH metric without addressing its material source, including its limiting cases as the corresponding small parameter tends to zero. We then show that QBHs can exist among self-gravitating configurations of electromagnetic and dilatonic scalar fields without matter. These general results are illustrated by explicit examples of exact solutions.