  Reconnections and interactions of filamentary coherent structures play a
fundamental role in the dynamics of fluids, plasmas and nematic liquid
crystals. In fluids, vortex reconnections redistribute energy and helicity
among the length scales and induce fine-scale turbulent mixing. Unlike ordinary
fluids where vorticity is a continuous field, in quantum fluids vorticity is
concentrated into discrete (quantized) vortex lines turning vortex
reconnections into isolated events, making it conceptually easier to study.
Here we report experimental and numerical observations of three-dimensional
quantum vortex interactions in a cigar-shaped atomic Bose-Einstein Condensate
(BEC). In addition to standard reconnections, already numerically and
experimentally observed in homogeneous systems away from boundaries, we show
that double reconnections, rebounds and ejections can also occur as a
consequence of the non-homogeneous, confined nature of the system.
