Critical velocity in He-3-B vibrating wire experiments as analog of vacuuminstability in a slowly oscillating electric field

The Lancaster experiments [C. A. M. Castelijns, K. F. Coates, A. M. Guenaul t, S. G. Mussett, and G. R. Pickett Phys. Rev. Lett. 56, 69 (1986)] with a cylindrical wire moving in superfluid He-3-B are discussed, where the measu red critical velocity of pair creation was much below the Landau critical v elocity. The phenomenon is shown to be analogous to the instability of the electron-positron vacuum in an adiabatically alternating strong electric po tential of both signs, where the positive-and negative-root levels cross an d thus the instability threshold is half the conventional value in a single static potential well. (C) 1999 American Institute of Physics. [S1063-7761 (99)00701-5].