  In super- or subradiance, a quantum superposition of excited atoms
collectively emits a photon much more or much less rapidly than an isolated
atom. Superradiant and subradiant lifetimes have been derived for finite
spheres of uniform media, either by simulating random samples or by expanding
in spherical harmonics and analyzing Bessel functions. We introduce a simple
regulator that applies to unbounded media, enabling trivial derivation and
analysis of lifetimes via elementary Fourier techniques. The regulator can be
interpreted as a correlation length for atomic positions; the regularized
system describes localized regions of enhanced radiative activity in otherwise
quiescent surroundings.
