Constraints on the generalized natural inflation after Planck 2018

TL;DR

This paper constrains the generalized natural inflation model using Planck 2018 and BICEP2/Keck data, showing it is favored within specific parameter ranges and analyzing the effects of reheating on its predictions.

Contribution

It provides new observational constraints on the GNI model parameters and discusses the impact of reheating phases on inflationary predictions.

Findings

GNI model is favored by current data within specific parameter ranges.

Reheating phase parameters significantly influence the model's behavior.

Constraints on scalar spectral index and tensor-to-scalar ratio are consistent with observations.

Abstract

Based on the dynamics of single scalar field slow-roll inflation and the theory of reheating, we investigate the generalized natural inflationary (GNI) model. Concretely, we give constraints on the scalar spectral index $n_{s}$ and tensor-to scalar ratio $r$ for $\Lambda$CDM $+r$ model according to the latest data from Plack 2018 TT,TE,EE+lowE+lensing (P18) and BICEP2/Keck 2015 season (BK15), i.e., $n_{s}=0.9659\pm0.0044$ at $68\%$ confidence level (CL) and $r<0.0623$ at $95\%$CL. We find that the GNI model is favored by P18 plus BK15 in the ranges of $\log_{10}(f/M_{p})=0.62^{+0.17}_{-0.18}$ and $m=0.35^{+0.13}_{-0.23}$ at $68\%$CL. In addition, the corresponding predictions of the general and two-phase reheating are respectively discussed. It follows that the parameter $m$ has the significant effect on the model behaviors.