1. INRIA Saclay-Île de France; F-91893 Orsay France
2. Université Paris Sud; F-91405 Orsay France
3. INRIA Rocquencourt; Alpines, B.P. 105 F-78153 Le Chesnay Cedex France
4. UPMC Univ Paris 06, CNRS UMR 7598, Laboratoire Jacques-Louis Lions; F-75005 Paris France
5. APC, Univ Paris Diderot, CNRS/IN2P3, CEA/Irfu, Obs de Paris; Sorbonne Paris Cité France