Scissors mode and superfluidity of a trapped Bose-Einstein condensed gas

We investigate the oscillation of a dilute atomic gas generated by a sudden rotation of the confining trap (scissors mode). This oscillation reveals t he effects of superfluidity exhibited by a Bose-Einstein condensate. The sc issors mode is also investigated in a classical gas above T-c in various co llisional regimes. The crucial difference with respect to the superfluid ca se arises from the occurrence of low frequency components, which are respon sible for the rigid value of the moment of inertia. Different experimental procedures to excite the scissors mode are discussed.