“…for an appropriate normalizing constant c. Here ǫ is the Levi-Civita symbol, i.e., Note that (1.1) is a generalization of the Lagrangian for wave maps, where here we have now introduced a coupling between maps U : R 1+3 → S 3 and 1-forms A on R 1+3 . Following [14,16,15], we consider only a restricted class of maps U and forms A, namely we make an equivariance assumption. Let (t, r, θ, φ) be polar coordinates on R 1+3 .…”