Decaying Vacuum Energy Research Articles

Dissipative cosmology with decaying vacuum energy.

A closed cosmological model that begins with a phase of generalized inflation followed by a Friedmann-like period is proposed.

Cosmology with decaying vacuum energy

Motivated by recent attempts to solve the cosmological constant problem, we examine the observational consequences of a vacuum energy which decays in time. In both radiation and matter dominated eras, the ratio of the vacuum to the total energy density of the universe must be small. Although the vacuum cannot provide the “missing mass” required to close the universe today, its presence earlier in the history of the universe could have important consequences. Element abundances from primordial nucleosynthesis require the ratio x = ϱ vac/( ϱ vac + ϱ rad) ⩽ 0.1 of neutrino (or equivalent light) species to exceed N ν > 4, a case ruled out in the standard cosmological model. If the vacuum decays into low energy photons, the lack of observed spectral distortions in the microwave background gives tighter bounds, x < 4 × 10 −4. In the matter-dominated era, the presence of a vacuum term may allow more time for growth of protogalactic perturbations.