  The variational theory of higher-power energy is developed for mappings
between Riemannian manifolds, and more generally sections of submersions of
Riemannian manifolds, and applied to sections of Riemannian vector bundles and
their sphere subbundles. A complete classification is then given for
left-invariant vector fields on 3-dimensional unimodular Lie groups equipped
with an arbitrary left-invariant Riemannian metric.
