Moment Dilations and Functional Calculus for Random Operators

Abstract: We develop a dilation theory for tuples of random operators on a Hilbert space. Their joint distribution defines a moment kernel by expectation of operator products. We prove that this kernel admits a dilation to a Cuntz family of isometries precisely when the associated shifted kernel is dominated in the positive-definite order. As consequences, we establish a mean-square version of von Neumann's inequality and construct a free functional calculus for random operators, extending from polynomials to the free disk algebra and the free Hardy algebra. These results extend classical dilation theory into a probabilistic setting and provide new tools for analyzing noncommutative random systems.