On optimality conditions in control of elliptic variational inequalities

Abstract. In the paper we consider optimal control of a class of strongly monotone variational inequalities, whose solution map is directionally differentiable in the control variable. This property is used to derive sharp pointwise necessary optimality conditions provided we do not impose any control or state constraints. In presence of such constraints we make use of the generalized differential calculus and derive, under a mild constraint qualification, optimality conditions in a "fuzzy" form. For strings, these conditions may serve as an intermediate step toward pointwise conditions of limiting (Mordukhovich) type. For membranes, however, limiting conditions cannot be derived in this way.


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