A system is characterized by the set Ω of all its possible states. At a
given time, all the properties of the system can be recovered from the
knowledge of the instantaneous state x ∈ Ω.
P. Collet
Centre de Physique Th´eorique
CNRS UMR 7644
Ecole Polytechnique
F-91128 Palaiseau Cedex (France)
collet@cpht.polytechnique.fr
