Fluctuations between the BCS and BEC Limits in the System of Ultracold Alkali Atoms

We investigate the fluctuations induced by time-dependent interchange between the Bardeen-Cooper-Schrieffer and Bose-Einstein condensation regimes in the ultracold gas of fermion atoms. Such crossover can be triggered by varying the external magnetic field across the Feshbach resonance. Experimental realization is usually done via very fast switching which leads to the nonequilibrium effects. In this paper we focus on the ground state properties. In particular, we analyze time dependence of the wave function and consider fluctuations of the order parameters.