Can An Unstable Vacuum Drive The Expansion Of The Universe?

Is the expansion of the Universe a natural effect due to the internal dynamical properties of the physical vacuum? Can one rule out the possibility that the vacuum is unstable (or metastable) and naturally expands emitting conventional matter and energy similarly to a form of latent heat? Such a scenario based on new physics would deeply transform Cosmology and, in particular, make useless the notion of dark energy as well as the standard cosmological constant.