Non-minimally coupled Natural Inflation: Palatini and Metric formalism with the recent BICEP/Keck

Abstract

In this work, we show the effect of the non-minimal coupling $\xi {\varphi }^{2}R$ on the inflationary parameters by considering the single-field inflation and present the inflationary predictions of the appealing potential for the particle physics viewpoint: Natural Inflation, an axion-like inflaton which has a cosine-type periodic potential and the inflaton naturally emerges as a pseudo-Nambu-Goldstone boson with a spontaneously broken global symmetry. We present the inflationary predictions for this potential, $n_s$, $r$, and $\alpha =\mathrm{d}{n}_s/\mathrm{d}\ln k$. In addition, we assume standard thermal history after inflation, and using this, for considered potential, we show compatible regions for the $n_s$, $r$ within the recent BICEP/Keck results.

Comments: 1+14 pages, 9 figures. Comments are welcome