Axion-driven hybrid inflation over a barrier

TL;DR

This paper proposes a novel inflationary model driven by an axion-like field that involves a potential barrier and a waterfall transition, linking inflation, dark matter, and the Peccei-Quinn scale.

Contribution

It introduces a new axion-driven hybrid inflation scenario with a barrier that separates inflation from the waterfall transition, connecting cosmological observations with particle physics scales.

Findings

Inflationary Hubble parameter varies widely within the model.

Inflaton decay constant is below the Planck scale.

Model links dark matter candidates and the Peccei-Quinn scale.

Abstract

We present a scenario where an axion-like field drives inflation until a potential barrier, which keeps a waterfall field at the origin, disappears and a waterfall transition occurs. Such a barrier separates the scale of inflation from that of the waterfall transition. We find the observed spectrum of the cosmic microwave background indicates that the decay constant of the inflaton is well below the Planck scale, with the inflationary Hubble parameter spanning a wide range. Further, our model involves dark matter candidates including the inflaton itself. Also, for a complex waterfall field, we can determine cosmologically the Peccei-Quinn scale associated with the strong CP problem.