Friction Coefficient and Berry Phase for a Topological Singularity in a   Superfluid
  The coexistence of the universal transverse force and the non-universal friction force on a topological singularity in a superfluid is shown here. Based on the BCS type microscopic theory, we explicitly evaluate the quasiparticle contribution to the friction coefficient in a clean fermionic superfluid, showing a new feature of logarithmic divergence. 
X.-M. Zhu and P. Ao (Umea University)