[1] Sorbonne Univ, Lab Jacques Louis Lions, 4 Pl Jussieu, F-75005 Paris, France
[2] Univ South Carolina, Math Dept, 1523 Greene St, Columbia, SC 29208 USA
[3] Univ Bergen, Dept Math, Postbox 7803, N-5020 Bergen, Norway
[4] Inst Catalana Recerca & Estudis Avancats ICREA, Passeig Lluis Co 23, Barcelona 08010, Spain
[5] North Carolina State Univ, Dept Math, Campus Box 8205, Raleigh, NC 27965 USA