(1+2)-Dimensional Radially Symmetric Wave Maps Revisit

The author gives an alternative and simple proof of the global existence of smooth solutions to the Cauchy problem for wave maps from the (1+2)-dimensional Minkowski space to an arbitrary compact smooth Riemannian manifold without boundary, for arbitrary smooth, radially symmetric data. The author can also treat non-compact manifold under some additional assumptions which generalize the existing ones.