Cosmological vacuum decay, irreversible thermodynamics and event horizons

Abstract

We propose a new time evolution law for the cosmological `constant' in a spatially flat (k = 0) Friedmann-Lemaître-Robertson-Walker spacetime. From a thermodynamic model of the vacuum based upon work of Gibbons, Hawking and Davies, we obtain the law where r is the proper radius of the cosmological event horizon. From the field equations we can deduce a second-order differential equation for , that we solve numerically, showing that the cosmological `constant' problem could be solved phenomenologically. The decay of takes place during the deflationary era, and has the effect of creating a perfect fluid of strings. Finally, our model suggests a mechanism of destabilization of the de Sitter spacetime to explain the exit from inflation and the matter creation.