Quantum Nucleation of Phase Slips in a 1d Model of a Superfluid

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We use a 1d model of a superfluid based on the Gross-Pitaevskii Lagrangian to illustrate a general numerical method designed to find quantum tunneling rates in extended bosonic systems. Specifically, we study flow past an obstacle and directly solve the imaginary time dynamics to find the ``bounce'' solution connected with the decay of the metastable laminar state via phase slip nucleation. The action for the tunneling confuguration goes to zero at the threshold (in superfluid velocity) for classical production of these slips. Applications to other processes are briefly discussed.