Author: via Cintia Complesso Universitario di Monte S.Angelo 80126 Napoli, Italy e-mail n.fusco@unina.it Carlos E. Kenig Department of Mathematics University of Chicago 1118 E 58th Street, University Avenue Chicago IL 60637, USA e-mail: cek@math.uchicago.edu Fulvio Ricci Scuola Normale Superiore di Pisa Piazza dei Cavalieri 7 56126 Pisa, Italy e-mail: fricci@sns.it Gerard Van der Geer Korteweg-de Vries Instituut Universiteit van Amsterdam Plantage Muidergracht 24 1018 TV Amsterdam, The Netherlands e-mail: geer@science.uva.nl Cdric Villani Ecole Normale Suprieure de Lyon 46, alle dItalie 69364 Lyon Cedex 07 France e-mail: cvillani@umpa.ens-lyon.fr