A finite free energy density inSU(2) pure Yang-Mills thermodynamics

We show how monopoles, which are stabilized by quantum fluctuations and have a massM～T, contribute to yield an infrared finite expansion for the free energy density of Yang-Mills thermodynamics. The leading behaviour of this expansion is consistent with the perturbative one, but in higher orders it does involve both contributions, which are nonanalytic atg ²=0, and additional analytic terms, which are of nonperturbative origin.