English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We examine the gravitational collapse and black hole formation of multiplenon--spherical configurations constructed from Szekeres dust models withpositive spatial curvature that smoothly match to a Schwarzschild exterior.These configurations are made of an almost spherical central core regionsurrounded by a network of "pancake-like" overdensities and voids with spatialpositions prescribed through standard initial conditions. We show that a fullcollapse into a focusing singularity, without shell crossings appearing beforethe formation of an apparent horizon, is not possible unless the fullconfiguration becomes exactly or almost spherical. Seeking for black holeformation, we demand that shell crossings are covered by the apparent horizon.This requires very special fine-tuned initial conditions that impose verystrong and unrealistic constraints on the total black hole mass and fullcollapse time. As a consequence, non-spherical non-rotating dust sources cannotfurnish even minimally realistic toy models of black hole formation atastrophysical scales: demanding realistic collapse time scales yields hugeunrealistic black hole masses, while simulations of typical astrophysical blackhole masses collapse in unrealistically small times. We note, however, that theresulting time--mass constraint is compatible with early Universe models ofprimordial black hole formation, suitable in early dust-like environments.Finally, we argue that the shell crossings appearing when non-spherical duststructures collapse are an indicator that such structures do not form galacticmass black holes but virialise into stable stationary objects.

Black hole formation from the gravitational collapse of a non-spherical network of structures