QCD Axion Hybrid Inflation

Understand

When the inflaton is coupled to the gluon Chern-Simons term for successful reheating, mixing between the inflaton and the QCD axion is generally expected given the solution of the strong CP problem by the QCD axion.

• This is particularly natural if the inflaton is a different, heavier axion.
• We propose a scenario in which the QCD axion plays the role of the inflaton by mixing with heavy axions.
• In particular, if the energy scale of inflation is lower than the QCD scale, a hybrid inflation is realized where the QCD axion plays the role of the inflaton in early stages.