Echoes of $R^3$ modification and Goldstone preheating in the CMB-BAO landscape

TL;DR

Adding an $R^3$ term to inflationary models helps reconcile high spectral index observations with theoretical predictions and induces rapid preheating that aligns inflationary scales with CMB data.

Contribution

The paper demonstrates that an $R^3$ modification in inflationary models alleviates tension with observed spectral indices and triggers efficient Goldstone and Higgs preheating.

Findings

The $R^3$ term helps match the observed high $n_s$ with inflation models.

Preheating from Goldstone modes is rapid and supports observed CMB scales.

The modified model reduces tension between theory and observations.

Abstract

The $R^2$ and the single-field-like regime of $R^2$-Higgs inflation are disfavored by the observed high spectral index $n_s$ from the combined cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements at the $\sim2\sigma$ level. The addition of a dimension-six $R^3$ term in the action helps alleviate this tension. We show that the parameter space accounting for the observed high $n_s$ also induces rapid Goldstone and Higgs preheating. The preheating, especially from Goldstone modes, helps match the CMB and inflationary scales, which in turn supports the observed $n_s$.