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Perturbation theory for the matrix square root and matrix modulus (1810.01464v1)
Published 2 Oct 2018 in math.FA
Abstract: We provide first order perturbation formulas for the matrix square root (in the positive semi-definite case) and the matrix modulus (in the general case). The results are new for singular matrices, and extend previously known Fr\'{e}chet differentiability formulas provided by the Daleckii-Krein theorem.