Modulated Natural Inflation

TL;DR

This paper explores how string theory embedding of axionic inflation modifies the inflationary potential with modular functions, leading to observable deviations in the CMB power spectrum and compatibility with the weak gravity conjecture.

Contribution

It introduces a model-independent framework where string duality symmetries replace cosine potentials with modular functions, affecting inflation predictions.

Findings

Inflation potential exhibits 'wiggles' due to modular functions.

Scalar power spectrum deviates from standard power law.

Trans-Planckian axion excursions are compatible with the weak gravity conjecture.

Abstract

We discuss some model-independent implications of embedding (aligned) axionic inflation in string theory. As a consequence of string theoretic duality symmetries the pure cosine potentials of natural inflation are replaced by modular functions. This leads to "wiggles" in the inflationary potential that modify the predictions with respect to CMB-observations. In particular, the scalar power spectrum deviates from the standard power law form. As a by-product one can show that trans-Planckian excursions of the aligned effective axion are compatible with the weak gravity conjecture.