  Axion-like particles with a coupling to non-Abelian gauge fields at finite
temperature can experience dissipation due to sphaleron heating. This could
play an important role for warm inflation or dynamical dark energy. We
investigate to what degree the efficiency of this non-perturbative mechanism
depends on the details of the underlying particle physics model. For a wide
range of scenarios and energy scales, we find that a previously discussed
suppression of sphaleron heating by light fermions can be alleviated. As an
outlook, we point out that fermionic effects may provide a new mechanism for
ending warm inflation.
