An acoustic analog to the dynamical Casimir effect in a Bose-Einstein   condensate
  We have realized an acoustic analog to the Dynamical Casimir effect. The density of a trapped Bose-Einstein condensate is modulated by changing the trap stiffness. We observe the creation of correlated excitations with equal and opposite momenta, and show that for a well defined modulation frequency, the frequency of the excitations is half that of the trap modulation frequency. 
Jean-Christophe Jaskula (LCF), Guthrie B. Partridge (LCF), Marie   Bonneau (LCF), Rapha\"el Lopes (LCF), Josselin Ruaudel (L...
cond-mat.quant-gas