@article{1083.49023, author="Hinterm\"uller, M. and Kovtunenko, V. and Kunisch, K.", title="{Semismooth Newton methods for a class of unilaterally constrained variational problems.}", language="English", journal="Adv. Math. Sci. Appl. ", volume="14", number="2", pages="513-535", year="2004", abstract="{Summary: A class of semismooth Newton methods for quadratic minimization problems subject to non-negativity constraints resulting from discretizing classes of optimization problems in function spaces is considered. For the algorithm, which is equivalent to a primal-dual active set strategy, locally superlinear as well as global convergence results are established. The global convergence assertions rely on matrix properties which characterize classes of discretized differential operators. Further, under an M-matrix property monotonous convergence with respect to the constrained components of the primal iterates is established. A comprehensive report on numerical tests is provided for the scalar-valued problem with a boundary obstacle, the vector-valued Signorini problem with an obstacle, and the symmetric crack problem. The numerical results support the theoretical findings.}", keywords="{semismooth Newton methods; Lam\'e system; vector-valued Signorini problem; symmetric crack problem}", classmath="{*49M25 (Finite difference methods) 90C20 (Quadratic programming) 65K10 (Optimization techniques (numerical methods)) 74R10 (Brittle fracture) }", }