QFS 2016 Book of Abstracts

Abstracts

P3.2 Dynamics of quantized vortices before reconnection at finite temperature Andryushchenko Andrey, Kondaurova Luiza, Nemirovskii Sergey Institute of Thermophysics SB RAS, Lavrentyev ave, 1, 630090, Novosibirsk, Russia Novosibirsk and Novosibirsk University, Department of Physics The goal of this paper is to investigate the dynamics of quantized vortex loops, just before the reconnection at finite temperature. Modeling is performed on the base of vortex filament method. It was discovered that the initial position of vortices and the temperature strongly affect the dependence on time of the minimum distance δ ( t ) between tips of two vortex loops. However, this relationship takes a universal square-root form δ ( t ) = [( k/ 2 π ) ∗ ( t ∗ − t )] 1 / 2 at distances smaller than the distances, satisfying the Schwarz reconnection criterion, when the nonlocal contribution to the Biot–Savart equation becomes about equal to the local contribution. In the “universal” stage, the nearest parts of vortices form a pyramid-like structure with angles which neither depend on the initial configuration nor on temperature. P3.3 Theory of adiabatic fountain resonance with superfluid 4 He Gary A. Williams University of California, Los Angeles, CA 90095, USA The theory of ”adiabatic fountain resonance” with superfluid 4 He is clarified. In this geometry a film region between two silicon wafers glued at their outer edge opens up to a central region with a free surface. We find that the resonance in this system is not a Helmholtz resonance as claimed by Gasparini and co-workers, but in fact is a 4th sound resonance. It occurs at relatively low frequency because the thin silicon wafers flex appreciably from the pressure oscillations of the sound wave. We raise questions about the ”giant proximity effect” claimed to have been observed with this resonance.

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