Graph products of completely positive maps

Abstract

We define the graph product of unital completely positive maps on a universal graph product of unital C∗-algebras and show that it is unital completely positive itself. To accomplish this, we introduce the notion of the non-commutative length of a word, and we obtain a Stinespring construction for concatenation. This result yields the following consequences. The graph product of positive-definite functions is positive-definite. A graph product version of von Neumann's inequality holds. Graph independent contractions on a Hilbert space simultaneously dilate to graph independent unitaries.