Bulk viscosity of resonating fermions revisited: Kubo formula, sum rule, and the dimer and high-temperature limits

Abstract

The bulk viscosity of two-component fermions with a zero-range interaction is revisited both in two and three dimensions. We first point out that the "standard" Kubo formula employed in recent studies has flaws to give rise to an unphysical divergent bulk viscosity even in a limit where it is supposed to vanish. The corrected Kubo formula as well as the sum rule is then carefully rederived so as to confirm that the bulk viscosity indeed vanishes in the free, unitarity, and dimer limits. We also discuss that the recently found discrepancy between the Kubo formalism and the kinetic theory for the bulk viscosity is attributed to the fact that the quasiparticle approximation assumed by the latter breaks down even in the high-temperature limit.

12 pages, 3 figures; published version

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• General coordinate invariance and conformal invariance in nonrelativistic physics: Unitary Fermi gas
• Nonrelativistic conformal field theories
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• Viscosity and scale invariance in the unitary Fermi gas
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• Complex scaling flows in the quench dynamics of interacting particles
• Transport in p-wave interacting Fermi gases
• Microscopic derivation of the Boltzmann equation for transport coefficients of resonating fermions at high temperature
• Thermal conductivity of a weakly interacting Bose gas in quasi-one-dimension
• Bulk viscosity of resonantly interacting fermions in the quantum virial expansion
• Bulk viscosity of dual Bose and Fermi gases in one dimension
• Viscous Flow in a 1D Spin-Polarized Fermi Gas: the Role of Integrability on Viscosity
• Hydrodynamic attractor in periodically driven ultracold quantum gases
• Quantum transport in strongly correlated Fermi gases
• Viscous Drude weight of dual Bose and Fermi gases in one dimension