Boundary regularity of harmonic maps to nonpositively curved metric spaces

Gradient Flows on Nonpositively Curved Metric Spaces and Harmonic Maps

The notion of gradient flows is generalized to a metric space setting without any linear structure. The metric spaces considered are a generalization of Hilbert spaces, and the properties of such metric spaces are used to set up a finite-difference scheme of variational form. The proof of the Crandall–Liggett generation theorem is adapted to show convergence. The resulting flow generates a stro...

Summary of Gradient Flows on Nonpositively Curved Metric Spaces and Harmonic Maps

Gradient flows for energy functionals have been studied extensively in the past. Well known examples are the heat flow or the mean curvature flow. To make sense of the term gradient an inner product structure is assumed. One works on a Hilbert space, or on the tangent space to a manifold, for example. However, it is possible to do without an inner product. The domain of the energy functionals c...

Regularity of Harmonic Maps

Teichmüller harmonic map flow into nonpositively curved targets

The Teichmüller harmonic map flow deforms both a map from an oriented closed surface M into an arbitrary closed Riemannian manifold, and a constant curvature metric on M , so as to reduce the energy of the map as quickly as possible [16]. The flow then tries to converge to a branched minimal immersion when it can [16, 18]. The only thing that can stop the flow is a finite-time degeneration of t...

Boundary Regularity and the Dirichlet Problem for Harmonic Maps

In a previous paper [10] we developed an interior regularity theory for energy minimizing harmonic maps into Riemannian manifolds. In the first two sections of this paper we prove boundary regularity for energy minimizing maps with prescribed Dirichlet boundary condition. We show that such maps are regular in a full neighborhood of the boundary, assuming appropriate regularity on the manifolds,...