The Holstein-Primakoff mapping for pairs of bosons is extended in order to
accommodate single boson mapping. The proposed extension allows a variety of
applications and especially puts the formalism at finite temperature on firm
grounds. The new mapping is applied to the O(N+1) anharmonic oscillator with
global symmetry broken down to O(N). It is explicitly demonstrated that
N-Goldstone modes appear. This result generalizes the Holstein-Primakoff
mapping for interacting boson as developed in ref.[1].Comment: 9 pages, LaTeX. Physical content unchanged. Unnecessary figure
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