The shear viscosity of a trapped Bose-condensed gas

Exact time-averaged thermal conductance for small systems: Comparison between direct calculation and Green-Kubo formalism

“…The Green-Kubo (GK) formalism [28] has applications for many problems such as fluid slab flow properties [29], diffusion in granular fluids [30,31,32], fluctuation-dissipation theory [33,34], thermal conductance in condensed matter systems [35,36], viscosity of trapped Bose gas [37], triple-point bulk and shear viscosities [38,39] or selfdiffusion [40] for Lennard-Jones fluids, among others. The GK method depends crucially on the convergence of time integrations of flux-flux correlation functions.…”

Shear viscosity of p-wave superfluid Fermi gas with weak interaction at low temperatures

“…The shear and bulk viscosities of 6 Li in the weakcoupling limit, for temperatures near T c and zero have been calculated by Shahzamanian and Yavari for the swave superfluid [11,12]. They showed that the shear viscosity decreases as (1 − T /T c ) with temperature, when passing through the transition temperature, and goes to a constant at very low temperatures.…”

“…If we ignore the interaction between these two fluids the dominated viscosity hence, is that of the normal excitations. The value of the second viscosity is temperature independent and is proportional to the inverse of the square of scattering length in the limit of low temperatures, and in the near transition temperature behaves as inverse of the gap parameter [12].…”

“…The Kubo formulas approach has been used to calculate the shear and bulk viscosities of strongly interacting ultracold Fermi, Bose gases by Taylor and Randeria [10], Shahzamanian and Yavari [12]. The former derived sum rules for the shear and bulk viscosity spectral functions, η(w) and ζ(w), respectively, of any Bose or Fermi system with arbitrary two -body interaction, and also at unitarity, the bulk or second viscosity spectral function vanishes at all frequencies and all temperatures.…”

Shear viscosity and imperfect fluidity in bosonic and fermionic superfluids

“…At a qualitative level our Kubo calculations are consistent with this earlier work, but we also include additional transport coefficients. A Kubo formulation of the shear viscosity of a trapped Bose condensed gas was studied in [16] within the second order Beliaev approximation, but this analysis did not incorporate the contribution from anomalous Green's functions. This paper revisits this earlier work (albeit without a trap) and with the important inclusion of the anomalous Green's functions, which are a crucial component for a consistent treatment of superfluid transport.…”