Critical Velocity in 3He-B Vibrating Wire Experiments as Analog of   Vacuum Instability in a Slowly Oscillating Electric Field
  The Lancaster experiments with a cylindrical wire moving in superfluid 3He-B are discussed, where the measured critical velocity of pair creation is much below the Landau critical velocity. The phenomenon is shown to be analogous to the instability of the electron-positron vacuum in an adiabatically alternating strong electric potential of both signs, where the positive- and negative-root levels cross and thus the instability treshold is twice less than in the conventional case of a single static potential well. 
A. Calogeracos and G.E. Volovik