A unified scheme for treating generalized superselection sectors is proposed on the basis of the notion of selection criteria to characterize states of relevance to each specific domain in quantum physics, ranging from the relativistic quantum fields in the vacuum situations with unbroken and spontaneously broken internal symmetries, through equi- librium and non-equilibrium states (see [1] for details).This is achieved by the help of
carrowq and
qarrowc channels, the former of which determines the states to be selected and to be parametrized by the order parameters defined as the spectrum of the centre constituting the su- perselection sectors, and the latter of which provides, as classifying maps, the physical interpretations of selected states in terms of order parameters.
In algebraic quantum field theory the (inverse) temperature is shown to be a macroscopic order parameter to parametrize mutually dis- joint thermal sectors arising from the broken scale invariance under renormalization-group transformations.This is accomplished in a mathematical formalism for the consistent treatment of explicitly broken symmetries such as broken scale invari- ance, on the basis of a clear-cut criterion for the symmetry breakdown in a unified scheme for sectors proposed recently by the author.
On the basis of the mathematical notion of “micro-macro duality” for understanding mutual relations between microsopic quantum systems (micro) and their macroscopic manifestations (macro) in terms of the notion of sectors and order parameters, a general mathematical scheme is proposed for detecting the state-structure inside of a sector through measurement processes of a maximal abelian subalgebra of the algebra of observables. For this purpose, the Kac-Takesaki operators controlling group duality play essential roles, which naturally leads to the composite system of the observed system and the measuring system formulated by a crossed product. This construction of composite systems will be shown to make it possible for the micro to be reconstructed from its observational data as macro in the light of the Takesaki duality for crossed products.