Warm-assisted natural inflation

Understand

We consider natural inflation in a warm inflation framework with a temperature-dependent dissipative coefficient $\Gamma \propto T^3$.

• Natural inflation can be compatible with the Planck 2018 results with such warm assistance.
• With no a priori assumptions on the dissipative effect's magnitude, we find that the Planck results prefer a weak dissipative regime for our benchmark scale $f=5 M_{\rm pl}$, which lies outside the $2\sigma$ region in the cold case.
• The inflation starts in the cold regime and evolves with a growing thermal fluctuation that dominates over quantum fluctuation before the end of the inflation.