Eur. Phys. J. Special Topics 217, 169-175 (2013)
https://doi.org/10.1140/epjst/e2013-01765-7

Regular Article

Shear viscosity and spin sum rules in strongly interacting Fermi gases

Physik Department, Technische Universität München, 85747 Garching, Germany

Received: 14 September 2012
Revised: 15 January 2013
Published online: 11 March 2013

Abstract

Fermi gases with short-range interactions are ubiquitous in ultracold atomic systems. In the absence of spin-flipping processes the number of atoms in each spin species is conserved separately, and we discuss the associated Ward identities. For contact interactions the spin conductivity spectral function σ_s(ω) has universal power-law tails at high frequency. We derive the spin f-sum rule and show that it is not affected by these tails in d < 4 dimensions. Likewise the shear viscosity spectral function η(ω) has universal tails; in contrast they modify the viscosity sum rule in a characteristic way.