Cosmological Constraints on Rapid Roll Inflation

TL;DR

This paper constrains rapid roll inflation models using cosmological data, showing they can produce acceptable spectra with specific parameter bounds and providing a concrete warped throat brane inflation example.

Contribution

It introduces a general framework for constraining rapid roll inflation models with observational data, including a specific realization within string theory.

Findings

Constraints on spectral index: n_s < 1

Bounds on running: |α| < 0.01

Viable rapid roll inflation model within warped throat brane inflation

Abstract

We obtain cosmological constraints on models of inflation which exhibit rapid roll solutions. Rapid roll attractors exist for potentials with large mass terms and are thus of interest for inflationary model building within string theory. We constrain a general ansatz for the power spectrum arising from rapid roll inflation that, in the small field limit, can be associated with tree level hybrid potentials with variable mass terms and nonminimal gravitational coupling $\xi R\phi^2$. We consider perturbations generated through modulated reheating and/or curvaton mechanisms in place of the observationally unacceptable primary spectra generated by inflaton fluctuations in these models. The lack of a hierarchy amongst higher-order $k$-dependencies of the power spectrum results in models with potentially large runnings, allowing us to impose tight constraints on such models using CMB and LSS data. In particular, we find $n_s <1$ and $|\alpha| < 0.01$. We conclude with a concrete realization of rapid roll inflation within warped throat brane inflation that is in good agreement with current data.