Persisting black holes in a bouncing universe

Abstract

We analyze whether a black hole could exist and persist in a universe that goes through a phase of contraction, bounce and subsequent expansion. To this end, we investigate the comoving generalized McVittiemetric that represents an inhomogeneity embedded in Friedmann-Lemaître-Robertson-Walker universe and allows interaction with the cosmic fluid. We compute the trapping horizons, spacetime regions and determine the lightcone structure. The analysis of the causal structure leads us to conclude that a dynamical black hole survives the cosmological bounce and continues to exist in the expanding phase of the universe. This result implies that bouncing cosmologies admit black holes at all epochs and that these black holes might play some role in the expanding phase of the universe.