Calibrations and the size of Grassmann faces

Abstract

In the past fifteen years or so, convex geometry and the theory of calibrations have provided a deeper understanding of the behavior and singular structure ofm-dimensional area-minimizing surfaces inR n . Calibrations correspond to faces of the GrassmannianG(m,R n ) of orientedm-planes inR n , viewed as a compact submanifold of the exterior algebra Λ m R n . Large faces typically provide many examples of area-minimizing surfaces. This paper studies the sizes of such faces. It also considers integrands Φ more general than area. One result implies that form-dimensional surfaces inR n , with 2 ⩽m ⩽n − 2, for any integrand Φ, there are Φ-minimizing surfaces with interior singularities.