## Abstract

The unperturbed Hamiltonian for the Bose-Einstein condensate, which includes not only the first and second powers of the zero mode operators but also the higher ones, is proposed to determine a unique and stationary vacuum at zero temperature. From the standpoint of quantum field theory, it is done in a consistent manner that the canonical commutation relation of the field operator is kept. In this formulation, the condensate phase does not diffuse and is robust against the quantum fluctuation of the zero mode. The standard deviation for the phase operator depends on the condensed atom number with the exponent of -1/3, which is universal for both homogeneous and inhomogeneous systems.

Original language | English |
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Article number | 013613 |

Journal | Physical Review A - Atomic, Molecular, and Optical Physics |

Volume | 89 |

Issue number | 1 |

DOIs | |

Publication status | Published - 2014 Jan 16 |

## Keywords

- 03.75.Hh
- 03.75.Nt
- 67.85.-d

## ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics