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Physical Review A

Perturbation theory of spin-1 Bose-Einstein condensates

Shingo Ohtsuka, Susumu Kurihara

Published Jul 7, 2003• 6 citations
Publisher

Abstract

We generalize the perturbation theory of weakly interacting bosons to Bose-Einstein condensates with hyperfine spin $F=1.$ Analytical expressions of second-order self-energies beyond the mean-field approximation are derived at zero temperature. We further extend the perturbation theory to the finite-temperature case, and derive the corresponding self-energies. We evaluate these self-energies near the poles of the first-order (mean-field) Green's functions within the on-shell approximation, and expand the results in powers of wave number in the long-wavelength limit. Excitation spectra for each mode are obtained analytically at low temperatures. We also derive the ground-state energy and thermodynamic quantities such as free energy of the system.

DOI
10.1103/physreva.68.013601

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