Hall Viscosity and Angular Momentum in Gapless Holographic Models

We use the holographic approach to compare the Hall viscosity η_H and the angular momentum density J in gapless systems in 2+1 dimensions at finite temperature. We start with a conformal fixed point and turn on a perturbation which breaks the parity and time-reversal symmetries via gauge and gravitational Chern-Simons couplings in the bulk. While the ratio of η_H and J shows some universal properties when the perturbation is slightly relevant, we find that the two quantities behave differently in general. In particular, η_H depends only on infrared physics, while J receives contributions from degrees of freedom at all scales