CONTROLLABILITY OF A 2 x 2 PARABOLIC SYSTEM BY ONE FORCE WITH SPACE-DEPENDENT COUPLING TERM OF ORDER ONE

This paper is devoted to the controllability of linear systems of two coupled parabolic equations when the coupling involves a space dependent first order term. This system is set on an bounded interval I subset of subset of R, and the first equation is controlled by a force supported in a subinterval of I or on the boundary. In the case where the intersection of the coupling and control domains is nonempty, we prove null controllability at any time. Otherwise, we provide a minimal time for null controllability. Finally we give a necessary and sufficient condition for the approximate controllability. The main technical tool for obtaining these results is the moment method.