In this paper, we prove a Poincar\'e 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 closed and of Hausdorff dimension at most n−3, are
totally geodesic balls or spherical caps intersecting the unit sphere with
constant contact angle; for stable sets in a wedge-shaped domain or in a half
space, provided the same condition of the singular set, must be spherical. In
particular, they are smooth.Comment: 35 pages, 2 figures; added some arguments on stable measure-theoretic
capillary hyper surfaces in a half space or in a domain with planar
boundaries in section 6; typos correcte