Black hole formation in relativistic Oscillaton collisions

TL;DR

This paper explores how black holes form from collisions of oscillatons, revealing that small boosts can prevent black hole formation and identifying a stability band influenced by collision dynamics.

Contribution

It introduces the concept of a stability band in oscillaton collisions, showing how initial boosts affect black hole formation contrary to previous expectations.

Findings

Unboosted collisions form black holes if compactness > 0.035.

Small initial boosts prevent black hole formation despite high compactness.

High boosts lead to black hole formation consistent with the hoop conjecture.

Abstract

We investigate the physics of black hole formation from the head-on collisions of boosted equal mass Oscillatons (OS) in full numerical relativity, for both the cases where the OS have equal phases or are maximally off-phase (anti-phase). While unboosted OS collisions will form a BH as long as their initial compactness $\mathcal{C}\equiv GM/R$ is above a numerically determined critical value $\mathcal{C}>0.035$, we find that imparting a small initial boost counter-intuitively \emph{prevents} the formation of black holes even if $\mathcal{C}> 0.035$. If the boost is further increased, at very high boosts $\gamma>1/12\mathcal{C}$, BH formation occurs as predicted by the hoop conjecture. These two limits combine to form a "stability band" where collisions result in either the OS "passing through" (equal phase) or "bouncing back" (anti-phase), with a critical point occurring around ${\cal C}\approx 0.07$. We argue that the existence of this stability band can be explained by the competition between the free fall and the interaction timescales of the collision.