Scattering problems in a domain with small holes.
In this paper, we consider a family of scattering problems in perforated unbounded domains Ω. We assume that the perforation is contained in a bounded region and that the holes have a ?critical? size. We study the asymptotic behaviour of the outgoing solutions of the steady-state scattering problem and we prove that an extra term appears in the limit equation. Finally, we obtain convergence results for scattering frequencies and solutions.