The R-axion and non-Gaussianity

TL;DR

This paper explores how quantum fluctuations of the R-axion, a pseudo Nambu-Goldstone boson, can lead to observable non-Gaussian isocurvature perturbations in the early universe, linking particle physics with cosmological observations.

Contribution

It demonstrates the generation of large non-Gaussianity in dark matter isocurvature perturbations from R-axion fluctuations during inflation, with implications for inflation scale constraints.

Findings

R-axion fluctuations induce non-Gaussian isocurvature perturbations.

Constraints on inflation scale and initial misalignment are established.

Decay channels produce neutralino LSPs contributing to dark matter.

Abstract

We study cosmological implications of an R-axion, a pseudo Nambu-Goldstone boson associated with spontaneous breaking of an U(1)_R symmetry, focusing on its quantum fluctuations generated during inflation. We show that, in the anomaly mediation, the R-axion decays into a pair of gravitinos, which eventually decay into the visible particles producing the neutralino LSP. As a result, the quantum fluctuations of the R-axion are inherited by the cold dark matter isocurvature density perturbation with potentially large non-Gaussianity. The constraints on the inflation scale and the initial misalignment are derived.