Affiliations: Department of Mathematics and Systems Analysis, Aalto University, Aalto, Finland. E-mail: lucas.chesnel@doc.polytechnique.org | Laboratory Jacques Louis Lions, University Pierre et Marie Curie, Paris, France. E-mail: claeys@ann.jussieu.fr | Faculty of Mathematics and Mechanics, St. Petersburg State University, St. Petersburg, Russia. E-mail: srgnazarov@yahoo.co.uk
Note: [] Corresponding author: Lucas Chesnel, Department of Mathematics and Systems Analysis, Aalto University, P.O. Box 11100, FI-00076 Aalto, Finland. E-mail: lucas.chesnel@doc.polytechnique.org
Abstract: We study a 2D scalar harmonic wave transmission problem between a classical dielectric and a medium with a real-valued negative permittivity/permeability which models a metal at optical frequency or an ideal negative metamaterial. We highlight an unusual instability phenomenon for this problem when the interface between the two media presents a rounded corner. To establish this result, we provide an asymptotic expansion of the solution, when it is well-defined, in the geometry with a rounded corner. Then, we prove error estimates. Finally, a careful study of the asymptotic expansion allows us to conclude that the solution, when it is well-defined, depends critically on the value of the rounding parameter. We end the paper with a numerical illustration of this instability phenomenon.
