Collapses and explosions in self-gravitating systems

TL;DR

This study uses molecular dynamics simulations to analyze collapse and explosion transitions in self-gravitating systems, confirming mean-field predictions and revealing finite metastable state lifetimes.

Contribution

It provides detailed simulation evidence supporting mean-field theory predictions for collapse and explosion phenomena in self-gravitating systems.

Findings

Collapse occurs near the predicted energy threshold.

Explosions happen faster than collapses, within an order of magnitude.

Mean-field description matches simulation data within uncertainty.

Abstract

Collapse and reverse to collapse explosion transition in self-gravitating systems are studied by molecular dynamics simulations. A microcanonical ensemble of point particles confined to a spherical box is considered; the particles interact via an attractive soft Coulomb potential. It is observed that the collapse in the particle system indeed takes place when the energy of the uniform state is put near or below the metastability-instability threshold (collapse energy), predicted by the mean-field theory. Similarly, the explosion in the particle system occurs when the energy of the core-halo state is increased above the explosion energy, where according to the mean field predictions the core-halo state becomes unstable. For a system consisting of 125 -- 500 particles, the collapse takes about $10^5$ single particle crossing times to complete, while a typical explosion is by an order of magnitude faster. A finite lifetime of metastable states is observed. It is also found that the mean-field description of the uniform and the core-halo states is exact within the statistical uncertainty of the molecular dynamics data.