Vortices in a stirred Bose-Einstein condensate.

We stir with a focused laser beam a Bose-Einstein condensate of [sup 87]Rb atoms confined in a magnetic trap. We observe the formation of a single vortex for a stirring frequency exceeding a critical value. At larger rotation frequencies we produce states of the condensate for which up to eleven vortices are simultaneously present. We present measurements of the decay of a vortex array once the stirring laser beam is removed. [ABSTRACT FROM AUTHOR]