Evolution of a Bose-Einstein condensate of neutral atoms --- A field   theoretical approach
  The particle distribution in a Bose condensate under the trapping potential and its time evolution after switching off the trapping potential suddenly are calculated. We investigate the problem from the viewpoint of quantum field theory,using a model of self-interacting neutral boson field. Within the approximation of retainng the most dominant term in the Hamiltonian after applying the Bogoliubov replacement, we can calculate analytically the particle distribution as a function of space and time coordinates. 
Koichi Nakamura (Meiji University) and Yoshiya Yamanaka (Waseda   University Senior High School)