  We study an N-body Calogero model in the S_N-symmetric subspace of the
positive definite Fock space. We construct a new algebra of S_N-symmetric
operators represented on the symmetric Fock space, and find a natural
orthogonal basis by mapping the algebra onto the Heisenberg algebra. Our main
result is the bosonic realization of nonlinear symmetry algebra describing the
structure of degenerate levels of Calogero model.
