New bounds on vacuum decay in de Sitter space

Vacuum decay in de Sitter space is a process of great physical interest, as it allows to rule out cosmological models in the early and current Universe. Its rate may be described in terms of an instanton in Euclidean space called bounce and it is usually interpreted as thermally assisted quantum tunneling. According to analytical and numerical evidence in the literature, a bounce exists only for certain values of the Hubble parameter in single scalar field theories with Einstein-Hilbert gravity. In the present paper, we rely on a novel approach to provide more stringent bounds, which may be easily extended to theories with non-minimally coupled and quadratic gravity. An additional restriction is also derived, which specifically applies to the latter.