Identification of the Support of Nonsmoothness

We consider a class of nonlinear equations in function spaces for which the nonlinearity can be split into smooth and nonsmooth parts. Such problems arise in optimal control problems for parabolic partial differential equations with bound constraints on the control. In many situations the nonsmooth part acts on functions having support in a set of small measure. If this small set can be well identified one can exploit this structure and apply Newton-like methods away from the small set.