  We investigate the relationship between Hall viscosity, spin density and
response to geometric torsion. For the most general effective action for
relativistic gapped systems, the presence of non-universal terms implies that
there is no relationship between torsion response and Hall viscosity. We also
consider free relativistic and non-relativistic microscopic actions and again
verify the existence of analogous non-universal couplings. Explicit examples
demonstrate that torsion response is unrelated to both Hall viscosity and spin
density. We also argue that relativistic gapped theories must have vanishing
Hall viscosity in Lorentz invariant vacuums.
