  The holonomy of an SU(2) N-instanton in the x^4-direction gives a map from
R^3 into SU(2), which provides a good model of an N-Skyrmion. Combining this
map with the standard Hopf map from SU(2)=S^3 to S^2 gives a configuration for
a Hopf soliton of charge N. In this way, one may define a collective-coordinate
manifold for Hopf solitons. This paper deals with instanton approximations to
Hopf solitons in the Skyrme-Faddeev model, focussing in particular on the N=1
and N=2 sectors, and the two-soliton interaction.
