# Persistent Black Holes in Bouncing Cosmologies

## TL;DR

This paper investigates the theoretical possibility of black holes surviving a cosmological bounce, providing exact solutions and conditions for their persistence across different cosmological models and dimensions.

## Contribution

It introduces exact solutions for black hole networks in bouncing cosmologies and establishes criteria for their survival through the bounce.

## Key findings

- Black holes can persist through a cosmological bounce under certain conditions.
- Exact initial data solutions for black hole networks at the bounce are derived.
- Conditions for black hole survival and non-merging in various dimensions are identified.

## Abstract

In this paper we explore the idea that black holes can persist in a universe that collapses to a big crunch and then bounces into a new phase of expansion. We use a scalar field to model the matter content of such a universe {near the time} of the bounce, and look for solutions that represent a network of black holes within a dynamical cosmology. We find exact solutions to Einstein's constraint equations that provide the geometry of space at the minimum of expansion and that can be used as initial data for the evolution of hyperspherical cosmologies. These solutions illustrate that there exist models in which multiple distinct black holes can persist through a bounce, and allow for concrete computations of quantities such as the black hole filling factor. We then consider solutions in flat cosmologies, as well as in higher-dimensional spaces (with up to nine spatial dimensions). We derive conditions for the black holes to remain distinct (i.e. avoid merging) and hence persist into the new expansion phase. Some potentially interesting consequences of these models are also discussed.