Cyclic Inflation

TL;DR

This paper proposes a cyclic inflation model where scale-invariant fluctuations originate from thermal radiation during a contraction phase, avoiding transplanckian issues and leading to observable cosmological perturbations.

Contribution

It introduces a geodesically complete cyclic inflation model generating scale-invariant perturbations from thermal radiation in contraction, a novel approach compared to standard inflation.

Findings

Scale-invariant fluctuations generated during contraction

Model avoids transplanckian problem

Modes stretched to observable scales after multiple cycles

Abstract

We present an inflationary model that is geodesically complete and does not suffer from the transplanckian problem. In most inflationary models, massless (conformal) scalar field fluctuations in a deSitter background gives rise to a scale-invariant spectrum. In this work, we realize scale invariant perturbations from thermal fluctuations in (conformal) radiation during a radiation dominated contraction era prior to inflation. As the modes exit the Hubble radius during the contraction phase, scale invariant fluctuations are indeed generated. After many cycles, we enter into a power-law inflationary phase, that stretches the modes produced in the previous contraction phase to scales that we observe today.