Reversible decay of ring dark solitons
  We show how boundary effects can cause a Bose-Einstein condensate to periodically oscillate between a (circular) array of quantised vortex-antivortex pairs and a (ring) dark soliton. If the boundary is restrictive enough, the ring dark soliton becomes long-lived. 
L. A. Toikka and K.-A. Suominen
cond-mat.quant-gas