Gravitational Properties of Monopole Spacetimes Near the Black Hole Threshold

TL;DR

This paper investigates the transition from monopole spacetimes to black holes, revealing how causally distinct regions emerge and exploring entropy and collapse dynamics near the black hole threshold.

Contribution

It introduces a detailed analysis of monopole solutions approaching black hole formation, highlighting the emergence of horizons, entropy definitions, and naked black hole behavior.

Findings

Near-critical solutions exhibit entropy similar to black holes.

Causally distinct regions develop as the black hole limit is approached.

Matter pulses can induce monopole collapse into extremal black holes.

Abstract

Although nonsingular spacetimes and those containing black holes are qualitatively quite different, there are continuous families of configurations that connect the two. In this paper we use self-gravitating monopole solutions as tools for investigating the transition between these two types of spacetimes. We show how causally distinct regions emerge as the black hole limit is achieved, even though the measurements made by an external observer vary continuously. We find that near-critical solutions have a naturally defined entropy, despite the absence of a true horizon, and that this has a clear connection with the Hawking-Bekenstein entropy. We find that certain classes of near-critical solutions display naked black hole behavior, although they are not truly black holes at all. Finally, we present a numerical simulation illustrating how an incident pulse of matter can induce the dynamical collapse of a monopole into an extremal black hole. We discuss the implications of this process for the third law of black hole thermodynamics.