Treffer: Aspects of nonnormality for iterative methods
https://doi.org/10.1016/j.laa.2004.06.026
https://www.sciencedirect.com/science/article/abs/pii/S0024379504003027
https://core.ac.uk/display/81201208
https://research.aalto.fi/en/publications/publication(b0a19586-ebbc-440a-970b-446ed7ed55dc)/export.html
https://research.aalto.fi/en/publications/aspects-of-nonnormality-for-iterative-methods(b0a19586-ebbc-440a-970b-446ed7ed55dc).html
https://www.sciencedirect.com/science/article/pii/S0024379504003027
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The paper deals with the study of various aspects of nonnormality of matrices arising from the existence of some algorithms. First, the binormal matrices are introduced and the dimension of the set of binormal matrices is computed. A related circulant matrix structure is highlighted, and the polynomial normality for matrices are defined. The author discusses the solution of linear systems involving nonnormal matrices. It is proved that a linear system involving a binormal matrix can be solved by executing an optimal 3-term recurrence for normal matrices. Since polynomial normality of particular degree remains invariant under unitary similarity transformations, the unitary orbit of binormal matrices and polynomially normal matrices of moderate degree, are considered. Measures of nonnormality related to iterative methods are discussed and three algorithms for computing the minimal normal polynomial of a matrix are presented.