R-Transforms of Free Joint Distributions and Non-crossing Partitions
R-Transforms of Free Joint Distributions and Non-crossing Partitions
复制标题
自由联合分布和非交叉分区的 R 变换
DOI:
10.1006/jfan.1996.0011
复制
发表时间:
1996
影响因子:
1.7
通讯作者:
A. Nica
中科院分区:
文献类型:
--
作者:
A. Nica
Abstract We introduce an extension of the notion of R-transform , defined by D. Voiculescu, to ( free ) joint distributions , i.e., normalized linear functionals on algebras of non-commutative polynomials in several indeterminates. We point out that the R -transform has good behavior with respect to the operations of free product and free convolution of joint distributions. We prove that the explicit computation of the inverse- R -transform of a joint distribution is done via a formula of summation over the lattice of non-crossing partitions, which shows that the R -transform is the operator-theoretic counterpart of the “free cumulants” considered in the combinatorial approach of R. Speicher. Moreover, in connection to the equivariance of the multidimensional R -transform under rotations, we show that a natural free analogue of a classical result about rotations of independent random variables is holding.