# Small field models of inflation that predict a tensor-to-scalar ratio $r=0.03$

## TL;DR

This paper develops small field inflation models capable of predicting a tensor-to-scalar ratio of 0.03, aligning with upcoming observational bounds and offering an alternative to large field models.

## Contribution

The authors construct viable small field inflation models that predict a tensor-to-scalar ratio of 0.03, expanding the range of testable inflation scenarios.

## Key findings

- Models predict r=0.03 consistent with Planck data
- Higher r values require increased tuning and larger field excursions
- Upcoming experiments can test these small field models

## Abstract

Future observations of the cosmic microwave background (CMB) polarization are expected to set an improved upper bound on the tensor-to-scalar ratio of $r\lesssim 0.03$. Recently, we showed that small field models of inflation can produce a significant primordial gravitational wave signal. We constructed viable small field models that predict a value of $r$ as high as $0.01$. Models that predict higher values of $r$ are more tightly constrained and lead to larger field excursions. This leads to an increase in tuning of the potential parameters and requires higher levels of error control in the numerical analysis. Here, we present viable small field models which predict $r=0.03$. We further find the most likely candidate among these models which fit the most recent Planck data while predicting $r= 0.03$. We thus demonstrate that this class of small field models is an alternative to the class of large field models. The BICEP3 experiment and the Euclid and SPHEREx missions are expected to provide experimental evidence to support or refute our predictions.