Regular dilation on graph products of N

We extended the definition of regular dilation to graph products of NN, which is an important class of quasi-lattice ordered semigroups. Two important results in dilation theory are unified under our result: namely, Brehmer's regular dilation on NkNk and Frazho–Bunce–Popescu's dilation of row contractions. We further show that a representation of a graph product has an isometric Nica-covariant dilation if and only if it is ⁎-regular. A special case of our result was considered by Popescu, and we studied the connection with Popescu's work.