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Vortex reconnections and bounces in trapped atomic Bose-Einstein condensates.

Dalfovo F., Serafini S., Lamporesi G., Galantucci L., Barenghi C.F., Ferrari G.
  Mercoledì 28/09   10:00 - 13:00   Edificio Psicologia 2 - Aula 2B   II - Fisica della materia
Vortex dynamics and reconnections play a fundamental role in quantum turbulent flows. In particular, quantum vortex reconnections are responsible for the redistribution of energy amongst scales and represent the ultimate process for incompressible kinetic energy dissipation into acoustic modes. Experimentally, direct visualization of vortexline dynamics in elongated Bose-Einstein Condensates (BECs) has been recently achieved in Trento, suggesting the possibility of exploring the effects of vortex-vortex interaction. In this work we compare the experimental observations with numerical simulations based on the solution of the GrossPitaevskii equation for the condensate wave function inside an anisotropic harmonic trapping potential. In the simulations we observe different twovortex interaction regimes depending on the relative orientation and velocity of the vortices, their orbits and their initial distance: unperturbed precession around the centre of the condensate, bounce dynamics, double and single reconnection events. The key ingredients driving the dynamics are the antiparallel preferred alignment of the two vortices and the impact of density gradients. The last two factors are peculiar to nonhomogeneous trapped BECs, determining hence different reconnection dynamics with respect to homogeneous BECs. Experimental evidences are provided to support this physical picture.