Topological description of pure invariant states of the Weyl $C^{\ast }$-algebra

Abstract

In this work we study the topology of certain families of states of the Weyl $C^{\ast }$-algebra with finite degrees of freedom. We focus on families of pure states characterized by symmetries and a (semi-)regularity condition, and obtain precise topological descriptions through homeomorphisms with other explicit spaces. Of special importance are the families of pure, semi-regular states invariant under either continuous (plane-wave states) or discrete (Bloch-wave states) spatial translations, and the family of states invariant under discrete, mutually commuting spatial and momentum translations (Zak-wave states), all of which we completely characterize.

39 pages. Keywords: Weyl $C^{\ast }$-algebra, pure invariant states, topological phases, classification of states