Inflation without Inflaton(s)

TL;DR

This paper introduces a cosmological model where the early universe's rapid expansion and reheating are driven by energy transitions rather than scalar fields, potentially explaining inflation and the small vacuum energy.

Contribution

It presents a novel 'cascading universe' model that achieves inflation-like expansion and reheating through energy transitions, avoiding the need for fundamental scalar fields.

Findings

Reproduces a spectrum similar to slow-roll inflation.

Achieves successful reheating with reasonable temperature.

Generates observable gravitational wave spectrum.

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 results 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.