Matricial R-transform ✩

We study the addition problem for strongly matricially free random variables which generalize free random variables. Using operators of Toeplitz type, we derive a linearization formula for the matricial R-transform related to the associated convolution. It is a linear combination of Voiculescu’s R-transforms in free probability with coefficients given by internal units of the considered array of subalgebras. This allows us to view this formula as the matricial linearization property of the R-transform. Since strong matricial freeness unifies the main types of noncommutative independence, the matricial R-transform plays the role of a unified noncommutative analog of the logarithm of the Fourier transform for free, boolean, monotone, orthogonal, s-free and c-free independence. © 2011 Elsevier Inc. All rights reserved