
TL;DR
This paper investigates how confined geometries influence the shear viscosity contributed by phonons in superfluids, showing that boundary interactions significantly affect viscosity, especially in optical traps at low temperatures.
Contribution
It introduces a simplified model analyzing phonon boundary interactions and derives an effective shear viscosity proportional to trap size and phonon density.
Findings
Shear viscosity depends on boundary scattering and trap size.
Phonons not in equilibrium exert shear stress on boundaries.
Viscosity decreases with temperature in optical traps.
Abstract
We analyze the effect of restricted geometries on the contribution of Nambu-Goldstone bosons (phonons) to the shear viscosity, , of a superfluid. For illustrative purpose we examine a simplified system consisting of a circular boundary of radius , confining a two-dimensional rarefied gas of phonons. Considering the Maxwell-type conditions, we show that phonons that are not in equilibrium with the boundary and that are not specularly reflected exert a shear stress on the boundary. In this case it is possible to define an effective (ballistic) shear viscosity coefficient , where is the density of phonons and is a parameter which characterizes the type of scattering at the boundary. For an optically trapped superfluid our results corroborate the findings of Refs. \cite{Mannarelli:2012su, Mannarelli:2012eg}, which imply that…
Peer Reviews
No public reviews on file for this paper yet. If you reviewed it on a platform where reviews are public (OpenReview, ICLR, NeurIPS, ICML), you can paste yours below so the community can read it here.
Videos
No videos yet. Explain this paper in a talk, walkthrough, or lecture? Add one.
Taxonomy
TopicsAcoustic Wave Resonator Technologies · Quantum, superfluid, helium dynamics · Mechanical and Optical Resonators
