RELATION BETWEEN MICROSCOPIC AND MACROSCOPIC CHARACTERISTICS OF STATISTICAL SYSTEMS

Order parameters of physical systems and order indices of their densit y matrices are, respectively, macroscopic and microscopic characterisi cs of a statistical system. We claim that there are situations in whic h the index provides more information than the parameter. This is prov ed by the exhibition of an exactly solvable model of a Bose system wit h mid-range order for which the order parameter is zero but for which an order index changes continuously as the Hamiltonian is varied.