Nonground state condensates of ultracold trapped atoms

The population dynamics of a trapped Bose-Einstein condensate, subject to t he action of an oscillatory field, is studied. This field produces a modula tion of the trapping potential with the frequency close to the transition F requency between the ground state and an excited energy level. Unusual crit ical effects are found exhibiting sharp qualitative changes in the populati on dynamics. An effective averaged system is constructed explicitly illustr ating the occurrence of critical phenomena. The related critical indices ar e calculated.