Solving Cosmological Problems of Supersymmetric Axion Models in an Inflationary Universe

TL;DR

This paper explores how specific conditions in inflationary cosmology can resolve longstanding cosmological issues in supersymmetric axion models, emphasizing the role of the saxion field's initial amplitude and decay timing.

Contribution

It demonstrates that large initial saxion amplitudes and early decay can prevent gravitino, axino overproduction, and isocurvature fluctuations in supersymmetric axion models.

Findings

All cosmological problems can be avoided with appropriate saxion dynamics.

Large initial saxion amplitude during inflation is crucial.

Decaying saxion before nucleosynthesis prevents overproduction.

Abstract

We revisit inflationary cosmology of axion models in the light of recent developments on the inflaton decay in supergravity. We find that all the cosmological difficulties, including gravitino, axino overproduction and axionic isocurvature fluctuation, can be avoided if the saxion field has large initial amplitude during inflation and decays before big-bang nucleosynthesis.