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SUMMARY:Chaotic transients and on-off intermittency in spatiotemporal chao
 s - Erico L. Rempel \,  IEFM/ITA - Institute of Aeronautical Technology\, 
 Sao Jose dos Campos\, Brazil
DTSTART:20090505T120000Z
DTEND:20090505T130000Z
UID:TALK17700@talks.cam.ac.uk
CONTACT:Dr Geoffroy Lesur
DESCRIPTION:Spatiotemporal chaos (STC) refers to the state where a spatial
 ly extended system is chaotic in time and irregular in space. Several work
 s have tried to identify the mechanisms for transition to STC. As one vari
 es a control parameter (e.g.\, Reynolds number - Re)\, at some critical va
 lue the spatially homogeneous steady state becomes unstable with respect t
 o small perturbations\, giving rise to periodic oscillations. For increasi
 ng Re\, other instabilities lead to symmetry breaking of spatiotemporal pa
 tterns\, resulting in states that are disordered in space and time. There 
 are several different routes to spatiotemporal chaos. This work focuses on
  crisis transitions to STC. As a control parameter is increased\, the syst
 em undergoes a transition from quasiperiodicity to temporal chaos\, then t
 o spatiotemporal chaos\, after a global bifurcation. The resulting time se
 ries displays on-off intermittency\, characterized by random switching bet
 ween laminar and bursty phases. Nonattracting chaotic sets known as chaoti
 c saddles\, present in a chaotic attractor\, are shown to be responsible f
 or these phases. Prior to the transition to STC\, chaotic saddles are resp
 onsible for transient spatiotemporal chaos. The results are exemplified wi
 th two nonlinear partial differential equations with applications to fluid
 s and plasmas: the Kuramoto-Sivashinsky and the regularized long-wave equa
 tions. Possible applications to nonlinear dynamo theory are discussed.
LOCATION:MR14\, DAMTP\, Pav. F
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