We analytically study effects of density and phase fluctuations of quasi-one-dimensional degenerate atomic Bose gases in the mean-field as well as in the hard-core bosons regimes. We obtain the analytic expressions for dynamic structure factors in both the regimes. We also calculate single-particle density matrix and momentum distribution by taking care of the phase fluctuations upto fourth-order term, the density fluctuations as well as the non-condensate density in both the regimes. In the mean-field regime, there is a long-tail in the momentum distributions at large temperature, which can be used to identify the quasi-condensate from a pure condensate. The single-particle correlation functions of hard-core bosons is almost zero even at zero temperature due to the fermionization of the bosonic systems. Two-particle correlation function in the hard-core bosons regime shows many deep valleys at various relative separations. These valleys at various relative separations imply shell structure due to the Pauli blocking in real space.
We consider the dynamics of a large system of
N interacting bosons in the mean-field regime where the interaction is of order
1/N. We prove that the fluctuations around the nonlinear Hartree state are generated by an effective quadratic Hamiltonian in Fock space, which is derived from Bogoliubov's approximation. We use a direct method in the
N-particle space, which is different from the one based on coherent states in Fock space.
We consider the dynamics of a large system of
N interacting bosons in the mean-field regime where the interaction is of order
1/N. We prove that the fluctuations around the nonlinear Hartree state are generated by an effective quadratic Hamiltonian in Fock space, which is derived from Bogoliubov's approximation. We use a direct method in the
N-particle space, which is different from the one based on coherent states in Fock space.