Dynamics of finite and infinite self-gravitating systems with cold quasi-uniform initial conditions

TL;DR

This paper investigates the dynamics of self-gravitating systems with cold, quasi-uniform initial conditions, revealing differences between finite and infinite systems and highlighting phenomena like energy ejection and the applicability of mean-field models.

Contribution

It provides a detailed comparison of finite and infinite self-gravitating systems with cold initial conditions, emphasizing the role of energy ejection and assessing mean-field descriptions.

Findings

Finite systems can eject energy and mass before virialization.

Differences in dynamics between finite and infinite systems are clarified.

The validity of the Vlasov-Poisson mean-field approximation is discussed.

Abstract

Purely self-gravitating systems of point particles have been extensively studied in astrophysics and cosmology, mainly through numerical simulations, but understanding of their dynamics still remains extremely limited. We describe here results of a detailed study of a simple class of cold quasi-uniform initial conditions, for both finite open systems and infinite systems. These examples illustrate well the qualitative features of the quite different dynamics observed in each case, and also clarify the relation between them. In the finite case our study highlights the potential importance of energy and mass ejection prior to virialization, a phenomenon which has been previously overlooked. We discuss in both cases the validity of a mean-field Vlasov-Poisson description of the dynamics observed, and specifically the question of how particle number should be extrapolated to test for it.