Regensburg 2007 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 3: Critical phenomena and phase transitions

DY 3.1: Vortrag

Montag, 26. März 2007, 12:00–12:15, H2

Tricritical dynamix at the demixing-superfluid transition in ³He-⁴He mixtures — •Reinhard Folk¹ and Günter Moser² — ¹Institute fot theoretical Physics, University of Linz, Linz Austria — ²Department for Material Sciences, University of Salzburg, Salzburg, Austria

We calculate in two loop order the dynamical critical behavior at the tricritical point occuring in ³He-⁴He mixtures. Model F^′ introduced by Siggia and Nelson [Phys. Rev. B 15, 1427 (1977)] - already problematic in one loop order - is shown to lead to a divergence of the mass diffusion D in contradiction to experiments. Within the complex symmetric version this model (model E^⋆′) the dynamical critical exponents of the kinetic coefficients can be calculated exactly leading to a mass diffusion going to zero at the tricitical point as D(t_X)∼ t_X^1/2 (t_X the relative temperature distance at constant concentration) and the thermal diffusion ratio k_T∼ t_X⁻¹ diverges proportional to the concentration susceptibility in the experimental region.

Supported by the Austrian Fonds zur Förderung der wissenschaftlichen Forschung, project No P18592