Quantum decay of a superflow through a weak link in a thin tube

We present an analytic calculation for the quantum decay rate of a superflo w through a weak link in a one-dimensional (1D) Bose-Einstein condensate (B EC). Deriving an effective action for the phase difference across the weak link, we arrive at the well-known problem of a massive particle with dampin g in a periodic potential. It follows that the superfluid shows an algebrai c flow-pressure characteristic. Short wave length fluctuations lead to a re normalization of the interaction between the bosons. As a consequence, the quantum phase transition observed for a particle with damping is not presen t in the superfluid system. (C) 2000 Elsevier Science B.V. All rights reser ved.