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Mardi 17 juin 2014-14:00

Diptyque LPT

Guillaume Guéguen et Xavier Plat (doctorants LPT)

par Gabriel LeMarié - 17 juin 2014

Xavier Plat

Order-by-disorder in a frustrated four-leg spin tube and its consequences

After briefly reminding the idea of the order-by-disorder phenomenon, we show in a simple 1D model how it can have strong consequences with the appearance of a phase where fluctuations are strongly suppressed.

Guillaume Gueguen

Mixed lipid bilayers with locally varying spontaneous curvature and bending

A model of lipid bilayers made of a mixture of two lipids with different average compositions on both leaflets, is developed. A Landau hamiltonian describing the lipid-lipid interactions on each leaflet, with two lipidic fields ψ1 and ψ2, is coupled to a Helfrich one, accounting for the membrane elasticity, via both a local spontaneous curvature, which varies as C0+C1(ψ1−ψ2)/2, and a bending modulus equal to κ0+κ1(ψ1+ψ2)/2. This model allows us to define curved patches as membrane domains where the asymmetry in composition, ψ1−ψ2, is large, and thick and stiff patches where ψ1+ψ2 is large. These thick patches are good candidates for being lipidic rafts, as observed in cell membranes.

Post-scriptum :

Contact : G. Lemarié