Gravitational wave background from vacuum and thermal fluctuations during axion-like inflation

Understand

We revisit the framework of axion-like inflation in view of the possibility that the coupling of the inflaton to a non-Abelian topological charge density could lead to the generation of a rapidly thermalizing heat bath.

• Both dispersive (mass) and absorptive (friction) effects are included.
• For phenomenologically viable parameters, the system remains in a weak regime of warm inflation (thermal friction $\ll$ Hubble rate).
• For tensor perturbations we derive an interpolating formula that incorporates both vacuum and thermal production.