arXiv subjects
Publications and source records attributed to Stefan Ragnarsson.
Within the field of numerical multilinear algebra, block tensors are increasingly important. Accordingly, it is appropriate to develop an infrastructure that supports reasoning about block tensor computation. In this paper we establish concise notation that is suitable for the analysis and development of block tensor algorithms, prove several useful block tensor identities, and make precise the notion of a block tensor unfolding.
Well known connections exist between the singular value decomposition of a matrix A and the Schur decomposition of its symmetric embedding sym(A) = [ 0 A; A' 0]. In particular, if s is a singular value of A then +s and -s are eigenvalues of the symmetric embedding. The top and bottom halves of sym(A)'s eigenvectors are singular vectors for A. Power methods applied to A can be related to power methods applied to sym(A). The rank of sym(A) is twice the rank of A. In this paper we show how to embed a general order-d tensor A into an order-d symmetric tensor sym(A). Through the embedding we relate (a) power methods for A's singular values to power methods for sym(A)'s eigenvalues and (b) the rank of A to the rank of sym(A).