We sketch the process of emergence of a nonperturbative thermal
ground-state estimate for the deconfining phase of SU(2) Yang-Mills
thermodynamics in terms of an inert, adjoint scalar field $\phi$ and a
pure-gauge configuration. This process amounts to spatial
coarse-graining over both noninteracting, selfdual configurations of
topological charge modulus unity and trivial holonomy,
Harrington-Shepard calorons, and trivial-topology, plane wave
fluctuations. Next, we discuss the effective action for the
deconfining phase, which couples the coarse-grained incarnations of
those two topological sectors. Implications such as dynamical
gauge-symmetry breaking and the evolution of the effective coupling,
predicting a phase boundary, are treated. Residual, radiative
corrections in the deconfining phase are loop expanded with rapid
convergence. As a generic and simple radiatively generated quantity we
discuss the one-loop polarization tensor (longitudinal and transverse
parts) for the massless mode. Finally, we comment on physics
applications in the realm of low-temperature photon physics and,
sketching the physics of the two other phases (preconfining,
confining), we point out a possible mechanism for electroweak symmetry
breaking in the realm of pure SU(2) Yang-Mills theory.