On non-commutative spreadability

Abstract

We review some results on spreadable quantum stochastic processes and present the structure of some monoids acting on the index-set of all integers $\mathbb Z$. These semigroups are strictly related to spreadability, as the latter can be directly stated in terms of invariance with respect to their action. We are mainly focused on spreadable, Boolean, monotone, and $q$-deformed processes. In particular, we give a suitable version of the Ryll-Nardzewski Theorem in the aforementioned cases.