Minimizing Harmonic Maps on the Unit Ball with Tangential Anchoring

Abstract

Since the seminal work of Schoen-Uhlenbeck, many authors have studied properties of harmonic maps satisfying Dirichlet boundary conditions. In this article, we instead investigate regularity and symmetry of ${\mathbb{S}}^2-$valued minimizing harmonic maps subject to a tangency constraint in the model case of the unit ball in ${\mathbb{R}}^3$. In particular, we obtain a monotonicity formula respecting tangentiality on a curved boundary in order to show optimal regularity up to the boundary. We introduce novel sufficient conditions under which the minimizer must exhibit symmetries. Under a symmetry assumption, we present a delineation of the singularities of minimizers, namely that a mimimizer has exactly two point singularities, located on the boundary at opposite points.

47 pages, 5 figures