Horizons in matter: black hole hair vs. Null Big Bang

TL;DR

This paper investigates the types of matter compatible with black hole and cosmological horizons, revealing specific conditions on matter's pressure-to-density ratio and implications for horizon-originated cosmological models.

Contribution

It characterizes the matter types that can coexist with horizons, including vacuum, cosmic strings, and phantom matter, and discusses horizon-originated cosmological scenarios.

Findings

Vacuum and certain matter with specific w values can coexist with horizons.

Null Big Bang scenarios involve horizons with vacuum and phantom matter.

Normal matter is generated from vacuum in horizon-originated cosmologies.

Abstract

It is shown that only particular kinds of matter (in terms of the "radial" pressure to density ratio $w$) can coexist with Killing horizons in black-hole or cosmological space-times. Thus, for arbitrary (not necessarily spherically symmetric) static black holes, admissible are vacuum matter ($w=-1$, i.e., the cosmological constant or some its generalization) and matter with certain values of $w$ between 0 and -1, in particular, a gas of disordered cosmic strings ($w=-1/3$). If the cosmological evolution starts from a horizon (the so-called Null Big Bang scenarios), this horizon can co-exist with vacuum matter and certain kinds of phantom matter with $w\geq -3$. It is concluded that normal matter in such scenarios is entirely created from vacuum.