Instantons in four-dimensional gauged O(5) Skyrme models

We consider a family of four-dimensional nonlinear sigma models based on an O(5) symmetric group, whose fields take their values on the 4-sphere S-4. An SO(4)-subgroup of the model is gauged. The solutions of the model are ch aracterized by two distinct topological charges, the Chern-Pontryagin charg e of the gauge field and the degree of the map, i.e., the winding number, o f the S-4 field. The one-dimensional equations arising from the variation o f the action density subjected to spherical symmetry are integrated numeric ally. Several properties of the solutions thus constructed are pointed out. The only solution with unit Chern-Pontryagin charge are the usual BPST ins tantons with zero S-4 winding number, while solutions with unit S-4 winding number have zero Chern-Pontryagin charge. (C) 2001 American Institute of P hysics.