Is natural inflation in agreement with CMB data?

• Main Authors: Santos, F. B. M. dos, Rodrigues, G, Rodrigues, J. G, de Souza, R, Alcaniz, J. S
• Format: Journal Article
• Language: English
• Published: 21-04-2024
• Subjects: Physics - Cosmology and Nongalactic Astrophysics
• DOI: 10.48550/arxiv.2312.12286

Natural inflation is a well-motivated model for the early universe in which
an inflaton potential of the pseudo-Nambu-Goldstone form, $V(\phi) =
\Lambda^4[1 + \cos{(\phi/f)}]$, can naturally drive a cosmic accelerated epoch.
This paper investigates the observational viability of the minimally and
non-minimally coupled natural inflation scenarios in light of current Cosmic
Microwave Background (CMB) observations. We find that a small and negative
coupling of the field with gravity can alleviate the well-known observational
discrepancies of the minimally coupled model. We perform a Monte Carlo Markov
Chain analysis of the Planck 2018 CMB and BICEP/Keck Array B-mode polarization
data to estimate how strong the coupling $\xi$ should be to achieve concordance
with data. We also briefly discuss the impact of these results on the physical
interpretation of the natural inflation scenario.