dS4 universe emergent from Kerr-AdS5 spacetime: bubble nucleation catalyzed by a black hole.

The emergence of a four-dimensional de Sitter (dS4) universe on an expanding bubble in the five-dimensional anti-de Sitter (AdS5) background has been suggested as a possible cosmological scenario. It is motivated by the difficulties in the realization of a stable de Sitter vacua in string theory. The bubble can be nucleated in a meta-stable pure AdS5 spacetime, but it is known that a pure AdS spacetime is non-perturbatively unstable. It means that the pure AdS5 background is an idealized situation, and in realistic situations, non-linear perturbations in AdS may lead to the formation of black holes due to the gravitational turbulent instability. To investigate how the proposed scenario works in a more realistic situation, we here study the nucleation process of a vacuum bubble in the Kerr-AdS5 spacetime. Especially we investigate conditions sufficient to ensure the nucleation of a vacuum bubble with a rotating black hole and how the black hole affects the transition rate. We find that even in the Kerr-AdS5 spacetime, a quasi-dS4 expansion can be realized on the nucleated vacuum bubble without contradicting the de Sitter swampland conjectures. [ABSTRACT FROM AUTHOR]