Squeezing in the weakly interacting uniform Bose-Einstein condensate

摘要: We investigate the presence of squeezing in weakly repulsive uniform Bose gas, both condensate mode and nonzero opposite-momenta pairs, using two different variational formulations. explore U(1) symmetry breaking Goldstone's theorem context a squeezed coherent wavefunction, present associated Ward identity. show that is absent at mean field Hartree-Fock-Bogoliubov level emerges as result fluctuations about finite volume effect, which vanishes thermodynamic limit. On other hand, excitations survives limit interpreted terms density-phase variables number-conserving formulation interacting gas.