Vacuum energy and cosmological inflation

Abstract

We study the cosmic evolution from the perspective of the Running Vacuum Models, in which the vacuum energy density is dynamic throughout the cosmic history. In this context, we find that there is an initial period of inflation, in which the vacuum decays into radiation and there is a huge entropy production. In contrast to the standard inflaton-based mechanism of inflation, there is a smooth transition between this period and the standard ΛCDM radiation epoch. We also test the model against the Generalised Second Law, finding it is fulfilled in the current universe but not in the early stages. This is a welcome feature, however, as it may provide a possible solution to both the entropy and horizon problems, in a context where the eventual thermodynamic equilibrium of the universe is not jeopardised