Modular Invariant Slow Roll Inflation

TL;DR

This paper introduces new inflation models utilizing modular symmetry with the modulus field as the inflaton, predicting very small tensor-to-scalar ratios and specific spectral index running, aligning with cosmic microwave background data.

Contribution

It establishes a novel connection between modular inflation and stabilization, constrains potential shapes using symmetry, and explores parameter spaces consistent with observations.

Findings

Tensor-to-scalar ratio less than 10^{-6}

Spectral index running around 10^{-4}

Potential shapes strongly constrained by modular symmetry

Abstract

We propose new classes of inflation models based on the modular symmetry, where the modulus field $\tau$ serves as the inflaton. We establish a connection between modular inflation and modular stabilization, wherein the modulus field rolls towards a fixed point along the boundary of the fundamental domain. We find the modular symmetry strongly constrain the possible shape of the potential and identify some parameter space where the inflation predictions agree with cosmic microwave background observations. The tensor-to-scalar ratio is predicted to be smaller than $10^{-6}$ in our models, while the running of spectral index is of the order of $10^{-4}$.