Eur. Phys. J. C 24, 331-343 (2002)
DOI: 10.1007/s100520200914

Permutation invariant algebras, a Fock space realization and the Calogero model

S. Meljanac¹, M. Milekovic² and M. Stojic<sup>1

1</sup>  Rudjer Boskovic Institute, Bijenicka c.54, 10002 Zagreb, Croatia
²  Prirodoslovno-Matematicki Fakultet, Fizicki Zavod, P.O.B. 331, Bijenicka c.32, 10002 Zagreb, Croatia

(Received: 26 July 2001 / Revised version: 9 January 2002 / Published online: 12 April 2002 - © Springer-Verlag / Società Italiana di Fisica 2002 )

Abstract
We study permutation invariant oscillator algebras and their Fock space representations using three equivalent techniques, i.e. (i) a normally ordered expansion in creation and annihilation operators, (ii) the action of annihilation operators on monomial states in Fock space and (iii) Gram matrices of inner products in Fock space. We separately discuss permutation invariant algebras which possess hermitean number operators and permutation invariant algebras which possess non-hermitean number operators. The results of a general analysis are applied to the S_M-extended Heisenberg algebra, underlying the M-body Calogero model. Particular attention is devoted to the analysis of Gram matrices for the Calogero model. We discuss their structure, eigenvalues and eigenstates. We obtain a general condition for positivity of eigenvalues, meaning that all norms of states in Fock space are positive if this condition is satisfied. We find a universal critical point at which the reduction of the physical degrees of freedom occurs. We construct dual operators, leading to the ordinary Heisenberg algebra of free Bose oscillators. From the Fock-space point of view, we briefly discuss the existence of a mapping from the Calogero oscillators to the free Bose oscillators and vice versa.

© Società Italiana di Fisica, Springer-Verlag 2002