LOCAL A POSTERIORI ERROR ESTIMATES FOR CONVEX BOUNDARY CONTROL PROBLEMS.

In this paper, we derive some improved a posteriori error estimates for finite element approximation of Neumann boundary control problems. We first establish local upper a posteriori error estimates for both the state and the control approximation of the general convex boundary control problems. We then derive local upper and lower a posteriori error estimates for a class of control problems that frequently appear in applications. [ABSTRACT FROM AUTHOR]