Volume-constraint local energy-minimizing sets in a ball

In this paper, we prove a Poincare inequality for any volume-constraint local energy-minimizing sets, provided its singular set is of Hausdorff dimension at most $n-3$. With this inequality, we prove that the only volume-constraint local energy-minimizing sets in the Euclidean unit ball, whose singular set is of Hausdorff dimension at most $n-3$, are totally geodesic balls or spherical caps intersecting the unit sphere with constant contact angle. In particular, they are smooth.