A new well-defined velocity operator is proposed for the collective description of a many-boson system. It is show~ that the new velocity operator is irrotational. The Hamiltonian of the system is successfully described in terms of the density-fluctuation operator and the velocity operator. The interaction term in the order of N-' has a different form from that in previous papers. The range of validity of the present formalism is discussed in the final section in answer to the questions raised

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... o far on the collective formalism of the many-boson syste~.