2013/01/25 by Massimo Mannarelli, Mannarelli, Massimo
Engineering · Physics and Astronomy · #Acoustic Wave Resonator Technologies #FOS: Physical sciences #High Energy Physics - Phenomenology (hep-ph) #Mechanical and Optical Resonators #Quantum Gases (cond-mat.quant-gas) #Quantum, superfluid, helium dynamics #cond-mat.quant-gas #hep-ph
paper · pdf · doi:10.48550/arxiv.1301.6074
8 pages, 5 figures, talk given at the conference "Xth Quark Confinement and the Hadron Spectrum", October 8-12, 2012, TUM Campus Garching, Munich, Germany
arxiv created 2013/01/25 · openalex publication_date 2013/01/25 · arxiv updated 2013/01/28 · openalex created_date 2024/04/11 · openalex updated_date 2026/07/28
We analyze the effect of restricted geometries on the contribution of Nambu-Goldstone bosons (phonons) to the shear viscosity, η, of a superfluid. For illustrative purpose we examine a simplified system consisting of a circular boundary of radius R, 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 η∝ ρ\rm ph χR, where ρ\rm ph is the density of phonons and χ is a parameter which characterizes the type of scattering at the boundary. For an optically trapped superfluid our results corroborate the findings of Refs. \citeMannarelli:2012su, Mannarelli:2012eg, which imply that at very low temperature the shear viscosity correlates with the size of the optical trap and decreases with decreasing temperature.