Extended metastable dark energy

Abstract

The metastable dark energy scenario is revisited by assuming that the current false vacuum energy density is the remnant from a primeval inflationary stage. The zero temperature scalar field potential is here described by an even power series up to order six which depends on 3 free parameters: the mass of the scalar field ($m$), the dimensionless ($\lambda$) specifying the standard self-interaction term, and a free cutoff mass scale ($M$) quantifying all possible deviations from the degenerate false vacuum state. The current $\Lambda$CDM model is a consequence of the very long decay time of the false vacuum which although finite is much greater than the current age of the Universe. This result remains valid for arbitrary combinations of the $m/M$ ratio which can analytically be determined in the thin-wall approximation and numerically calculated outside this limit. Unlike many claims in the literature the vacuum dominance may be temporary. The finiteness of the decay time suggests that the ultimate stage of the observed Universe in such a scenario will not be driven by a de Sitter type cosmology.