1. INSA Rouen Normandie, Univ Rouen Normandie, CNRS, Normandie Univ, CORIA UMR 6614 1 , F-76000 Rouen, France
2. Institut Universitaire de France 2 , Rue Descartes, F-75231 Paris, France
3. Department of Mathematics, University of British Columbia 3 , Vancouver, British Columbia V6T1Z2, Canada