Cosmological expansion and local physics

TL;DR

This paper explores how cosmic expansion affects local gravitational systems, presenting new solutions for black holes in expanding universes and analyzing conditions for cosmic censorship violations.

Contribution

It introduces new exact solutions for black holes that are comoving with Friedmann universes and clarifies the limits of the all-or-nothing behavior in different cosmological backgrounds.

Findings

Weakly gravitating systems are comoving in de Sitter space.

New solutions describe black holes perfectly comoving with Friedmann universes.

Discussion on potential cosmic censorship violations near the Big Rip.

Abstract

The interplay between cosmological expansion and local attraction in a gravitationally bound system is revisited in various regimes. First, weakly gravitating Newtonian systems are considered, followed by various exact solutions describing a relativistic central object embedded in a Friedmann universe. It is shown that the ``all or nothing'' behaviour recently discovered (i.e., weakly coupled systems are comoving while strongly coupled ones resist the cosmic expansion) is limited to the de Sitter background. New exact solutions are presented which describe black holes perfectly comoving with a generic Friedmann universe. The possibility of violating cosmic censorship for a black hole approaching the Big Rip is also discussed.