69.
A variational problem with an obstacle for a certain class of quadratic functionals is considered. Admissible vector-valued
functions are assumed to satisfy the Dirichlet boundary condition, and the obstacle is a given smooth (
N − 1)-dimensional surface
S in ℝ
N
. The surface
S is not necessarily bounded.
It is proved that any minimizer
u of such an obstacle problem is a partially smooth function up to the boundary of a prescribed domain. It is shown that the
(
n − 2)-Hausdorff measure of the set of singular points is zero. Moreover,
u is a weak solution of a quasilinear system with two kinds of quadratic nonlinearities in the gradient. This is proved by
a local penalty method. Bibliography: 25 titles.
Dedicated to V. A. Solonnikov on the occasion of his jubilee
Published in
Zapiski Nauchnykh. Seminarov POMI, Vol. 362, 2008, pp. 15–47.
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