[1] Univ Massachusetts, Dept Math & Stat, Amherst, MA 01003 USA
[2] CALTECH, Dept Phys, Pasadena, CA 91125 USA
[3] CALTECH, Ctr Phys Informat, Pasadena, CA 91125 USA
[4] San Diego State Univ, Dept Math & Stat, Nonlinear Dynam Syst Grp, San Diego, CA 92182 USA
[5] Univ Athens, Dept Phys, Athens 15784, Greece