Dark energy from coexistence of phases

Abstract

We suggest that the current acceleration of the universe may be explained by the vacuum energy of a hidden sector which is stuck in a state of equilibrium between phases. The phases are associated to a late-time first-order phase transition, where phase coexistence originates at a temperature $T_c\sim 10^{-3}eV$ and lasts until temperature falls below $T\sim 10^{-4}eV$. During phase coexistence, the energy density has an effective cosmological constant component with the observed magnitude. This scenario does not require supercooling and may arise naturally in realistic models.

Comments: 11 pages. Contents significantly enlarged to make explanations clearer. Conclusions unchanged