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Personne :
Dubé, Louis J.

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Dubé

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Louis J.

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Université Laval. Département de physique, de génie physique et d'optique

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ncf11850600

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Résultats de recherche

Voici les éléments 1 - 6 sur 6
  • PublicationAccès libre
    Light-induced chaotic rotations in nematic liquid crystals
    (American Physical Society through the American Institute of Physics, 2006-02-23) Brasselet, Étienne.; Dubé, Louis J.
    Various nonlinear rotation regimes are observed in an optically excited nematic liquid-crystal film under boundary conditions for the light and material that are invariant by rotation. The excitation light is circularly polarized, the intensity profile is circularly symmetric, and the beam diameter at the sample location is a few times smaller than the cell thickness. A transition to chaos via quasiperiodicity is identified when the light intensity is taken as the control parameter. Transverse nonlocal effects are suggested to be the cause of the observed dynamics, and a simple model consisting of a collection of coupled rotators is developed to provide a qualitative explanation.
  • PublicationAccès libre
    Le chaos
    (Association canadienne-française pour l'avancement des sciences, 1997-03-01) Dubé, Louis J.
  • PublicationRestreint
    The control of hamiltonian chaos
    (Canadian association of physicists, 2001-03-01) Pourbohloul, Babak; Després, Philippe; Dubé, Louis J.; Doyon, Bernard
    We demonstrate the control of the chaotic dynamics of Hamiltonian systems. This ability offers the possibility to select (stabilize) at will regular behavior(s) within the chaotic regime and to make efficient use of the richness and diversity of chaos.
  • PublicationRestreint
    Chaotic rotations generated by light in nematic liquid crystals
    (Gordon and Breach, 2006-09-22) Brasselet, Étienne.; Dubé, Louis J.
    Various nonlinear rotation regimes are observed in an optically excited nematic liquid crystal film under boundary conditions (for the light and the material) that are invariant by rotation. Th excitation light is circularly polarized, the intensity profile is circularly symmetric and the beam diameter at the sample location is a few times smaller than the cell thickness. A transition to chaos via quasiperiodicity is identified when the light intensity is taken as the control parameter. Transverse nonlocal effects are suggested to be the cause of the observed dynamics and a simple model consisting of a collection of coupled rotators is developed to provide a qualitative explanation.
  • PublicationAccès libre
    Targeting unknown and unstable periodic orbits
    (American Institute of Physics, 2002-03-07) Dubé, Louis J.; Doyon, Bernard
    We present a method to target and subsequently control (if necessary) orbits of specified period but otherwise unknown stability and position. For complex systems where the dynamics is often mixed [e.g., coexistence of regular and chaotic regions in area-preserving (Hamiltonian) systems], this targeting algorithm offers a way to not only gently bring the system from the chaotic domain to an unstable periodic orbit (where control is applied), but also to access stable regions of phase space (where control is not necessary) from within the stochastic regions. The technique is quite general and applies equally well to dissipative or conservative discrete maps and continuous flows.
  • PublicationAccès libre
    On Jacobian matrices for flows
    (American Institute of Physics, 2005-02-10) Dubé, Louis J.; Doyon, Bernard
    We present a general method for constructing numerical Jacobian matrices for flows discretized on a Poincaré surface of section. Special attention is given to Hamiltonian flows where the additional constraint of energy conservation is explicitly taken into account. We demonstrate the approach for a conservative dynamical flow and apply the technique for the general detection of periodic orbits.