Inflation without inflaton(s)

Abstract

We propose a model for early universe cosmology without the need for fundamental scalar fields. Cosmic acceleration and phenomenologically viable reheating of the universe result from a series of energy transitions, where during each transition vacuum energy is converted to thermal radiation. We show that this ‘cascading universe’ can lead to successful generation of adiabatic density fluctuations and an observable gravity wave spectrum in some cases, where in the simplest case it reproduces a spectrum similar to slow-roll models of inflation. We also find the model provides a reasonable reheating temperature after inflation ends. This type of model may also be relevant for addressing the smallness of the vacuum energy today.