Beyond black holes: Universal properties of 'ultra-massive' spacetimes

TL;DR

This paper explores the universal properties of ultra-massive spacetimes with positive cosmological constant, revealing that they develop generalized holographic screens with maximal area, impacting black hole physics and cosmology.

Contribution

It demonstrates that spacetimes with large stable marginally trapped surfaces exhibit universal structures like holographic screens with maximal area, a novel insight into their geometry and evolution.

Findings

Existence of generalized holographic screens with maximal area $4\pi/\Lambda$

Universal behavior of MTSs in ultra-massive spacetimes

Implications for black hole mergers and cosmological models

Abstract

It has been long known that in spacetimes with a positive cosmological constant $\Lambda >0$ the area of spatially stable marginally trapped surfaces (MTSs) has a finite upper bound given by $4\pi/\Lambda$. In this paper I show that any such spacetime containing spatially stable MTSs with area approaching indefinitely that bound acquire universal properties generically. Specifically, they all possess {\em generalized} `holographic screens' (i.e. marginally trapped tubes) foliated by MTSs of spherical topology, composed of a dynamical horizon portion and a timelike membrane portion that meet at a distinguished round sphere $\bar S$ with constant Gaussian curvature $\mathcal{K} =\Lambda$ -- and thus of maximal area $4\pi/\Lambda$. All future (past) generalized holographic screens containing $\bar S$ change signature at $\bar S$, and all of them continue towards the past (future) with non-decreasing (non-increasing) area of their MTSs. A future (past) singularity obtains. For the future case, these `ultra-massive spacetimes' (arXiv:2209.14585) may be more powerful than black holes, as they can overcome the repulsive $\Lambda$-force and render the spacetime as a collapsing universe without event horizon enclosing those generalized holographic screens. It is remarkable that these behaviours do not arise if $\Lambda$ is non-positive. The results have radical implications on black hole mergers and on very compact objects accreting mass from their surroundings -- if $\Lambda >0$.