Can power spectrum observations rule out slow-roll inflation?

TL;DR

Future power spectrum observations could potentially falsify canonical single-field slow-roll inflation if they accurately measure spectral index running over a wide range of scales, despite current limitations.

Contribution

This study assesses the potential of future observations to rule out slow-roll inflation models based on spectral index measurements.

Findings

Current measurements are unlikely to falsify slow-roll inflation.

Future wide-scale observations could constrain or rule out slow-roll models.

Large parameter space remains viable under current observational constraints.

Abstract

The spectral index of scalar perturbations is an important observable that allows us to learn about inflationary physics. In particular, a detection of a significant deviation from a constant spectral index could enable us to rule out the simplest class of inflation models. We investigate whether future observations could rule out canonical single-field slow-roll inflation given the parameters allowed by current observational constraints. We find that future measurements of a constant running (or running of the running) of the spectral index over currently available scales are unlikely to achieve this. However, there remains a large region of parameter space (especially when considering the running of the running) for falsifying the assumed class of slow-roll models if future observations accurately constrain a much wider range of scales.