Natural Inflation After Planck 2018

Abstract

We calculate high-precision constraints on Natural Inflation relative to current observational constraints from Planck 2018 + BICEP/Keck(BK15) Polarization + BAO on $r$ and $n_S$, including post-inflationary history of the universe. We find that, for conventional post-inflationary dynamics, Natural Inflation with a cosine potential is disfavored at greater than 95\% confidence out by current data. If we assume protracted reheating characterized by $\overline{w}>1/3,$ Natural Inflation can be brought into agreement with current observational constraints. However, bringing unmodified Natural Inflation into the 68\% confidence region requires values of $T_{\mathrm{re}}$ below the scale of electroweak symmetry breaking. The addition of a SHOES prior on the Hubble Constant $H_0$ only worsens the fit.

13 pages, 4 figures (v2: References added)

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Cited by in corpus (6)

• Natural-Scalaron Inflation
• Natural Inflation with non minimal coupling to gravity in $R^2$ gravity under the Palatini formalism
• Completely Dark Matter from Rapid-Turn Multifield Inflation
• Non-minimally coupled Natural Inflation: Palatini and Metric formalism with the recent BICEP/Keck
• Connecting Cosmic Inflation to Particle Physics with LiteBIRD, CMB-S4, EUCLID and SKA
• Spectral Distortions from Axion Monodromy Inflation