Warm-assisted natural inflation
Yakefu Reyimuaji, Xinyi Zhang
Abstract
Abstract We consider natural inflation in a warm inflation framework with a temperature-dependent dissipative coefficient Γ∝ 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 pl , which lies outside the 2σ 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. The observed spectral tilt puts stringent constraints on the model's parameter space. We find that f< 1 M_ pl is excluded. A possible origin of such dissipative coefficient from axion-like coupling to gauge fields and tests of the model are also discussed.