Bose-Einstein Condensate: A Superposition of Macroscopically Squeezed States

摘要

We study the ground state of a uniform Bose gas at zero temperature in theHartree-Fock-Bogoliubov (HFB) approximation. We find a solution of the HFBequations which obeys the Hugenholtz-Pines theorem. This solution imposes amacroscopic squeezing to the condensed state and as a consequence displayslarge particle number fluctuations. Particle number conservation is restored bybuilding the appropriate U(1) invariant ground state via the superposition ofthe squeezed states. The condensed particle number distribution of this newground state is calculated as well as its fluctuations which present a normalbehavior.