Large Field and Small Field Inflation Models in Confrontation with Planck2018 and BICEP2018 Datasets

We study the non-minimal inflation with both the large field and small field potentials in the context of the new observational data. We analyze the linear and non-linear perturbations to obtain the scalar spectral index, tensor-to-scalar ratio, and nonlinearity parameter. By performing a numerical analysis on the scalar spectral index and tensor-to-scalar ratio, and comparing the results with Planck2018 TT, TE, EE+lowE+lensing+BAO+BK14(18) data, we find that the non-minimal large field inflation is observationally viable if the non-minimal coupling parameter is of the order of $10^{-3}$. The same analysis on the non-minimal small field inflation gives the values for the non-minimal coupling parameter as $10^{-4}$. We also study the non-Gaussian features in both equilateral and orthogonal configurations for large and small field potentials and find small values for these amplitudes, consistent with Planck2018 TTT, EEE, TTE and EET data. We show that the absolute values of the non-linearity parameter, $f_{NL}$, is larger in large field inflation than the small field model for both configurations. Also, we obtain more severe constraints on the parameter $p$ in the introduced large field and small field potentials with respect to previously reported constraints.