On Warm Natural Inflation and Planck 2018 Constraints

We investigate natural inflation with non-minimal coupling to gravity, characterized either by a quadratic or a periodic term, within the warm inflation paradigm during the slow-roll stage, in both strong and weak dissipation limits; and show that, in the case of a T-linearly dependent dissipative term, it can accommodate the spectral index n(s) and tensor-to-scalar ratio r observables given by Planck 2018 constraints, albeit with a too-small value of the e-folding number to solve the horizon problem, providing, thus, only a partial solution to natural inflation issues, assuming a T-cubically dependent dissipative term can provide a solution to this e-folding number issue.

Automated summary

We investigate natural inflation within the warm inflation paradigm, considering non-minimal coupling to gravity and both strong and weak dissipation limits. We show that for a T-linearly dependent dissipative term, it can accommodate the observables n(s) and r given by Planck 2018 constraints, but with a too-small e-folding number to solve the horizon problem. A T-cubically dependent dissipative term may provide a solution to this e-folding number issue.