Fluctuations of Bose-Einstein Condensate

Abstract

We study the ground state occupation number and its fluctuations for the Bose-Einstein condensate of trapped atoms using the microcanonical ensemble. The analytic formulas are obtained with the help of the saddle point method. We show that microcanonical fluctuations below the critical temperature tend to zero and scale with the number of particles as $1/\sqrt{N}$.