S. Nicaise, BOUNDARY EXACT CONTROLLABILITY OF TRANSMI SSION PROBLEMS WITH SINGULARITIES, Comptes rendus de l'Academie des sciences. Serie 1, Mathematique, 320(6), 1995, pp. 663-668
We prove the exact controllability by boundary action of hyperbolic tr
ansmission problems with singularities. The idea is to replace the cla
ssical space of controls by the space of their regular parts, which is
augmented with the coefficients of singularities. This lends to a cla
ssical boundary control but with an internal control, which is a distr
ibution with a support equal to the singular vertices.