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Prog. Theor. Phys. Vol. 57 No. 2 (1977) pp. 393-409

[ Full Text PDF : FREE ACCESS (1345K) ]

Collective Variable Approach to Many-Boson Systems at High Density

Toshiyuki Nishiyama and Masakazu Tsujii

Department of Physics, College of General Education, Osaka University, Toyonaka 560

(Received August 7, 1976)

Abstract:

Green's functions of phonons for many-boson systems at high density are obtained from the phonon Hamiltonian given in a previous paper on the basis of the coherent-state representation. A dispersion equation derived from these Green's functions gives rise to the excitation spectrum leading to the Feynman energy in the low-momentum limit. It is shown that the dynamic structure function obtained here satisfies the sum rules in the low-momentum limit. As an illustrative example, the one-dimensional Lieb-Liniger model is considered. The relationships to the previous theories, in particular, to the velocity field approach of Yamasaki, Kebukawa and Sunakawa and to our density and phase operator approach are elucidated by the use of a unitary transformation. Discussion will be made on the D-wave portion of the roton-roton interaction in relation to the resonance state of roton pair studied in one of our previous papers. Finally, it is pointed out that the zeroth Fourier transform of the phase operator is related to the superfluid velocity in the two-fluid theory of liquid helium II.


URL : http://ptp.ipap.jp/link?PTP/57/393/
DOI : 10.1143/PTP.57.393

[ Full Text PDF : FREE ACCESS (1345K) ] Citation:

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Citing Article(s) :

  1. Progress of Theoretical Physics Vol. 62 No. 5 (1979) pp. 1215-1224 :
    Momentum Distribution of a Charged Bose Gas at High Density
    Toshiyuki Nishiyama and Yoiti Watanabe
  2. Progress of Theoretical Physics Vol. 64 No. 5 (1980) pp. 1565-1576 :
    Momentum Distribution and Ground-State Energy of Liquid 4He at the Absolute Zero Temperature
    Toshiyuki Nishiyama and Yoiti Watanabe

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