On the 2-norm distance from a~normal matrix to the set of matrices with a~multiple zero eigenvalue
Zapiski Nauchnykh Seminarov POMI, Computational methods and algorithms. Part XVIII, Tome 323 (2005), pp. 50-56

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An elementary proof is given for a formula for the 2-norm distance from a normal matrix $A$ to the set of matrices with a multiple zero eigenvalue. Earlier, the authors obtained this formula as an implication of a nontrivial result due to A. N. Malyshev.
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     title = {On the 2-norm distance from a~normal matrix to the set of matrices with a~multiple zero eigenvalue},
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Kh. D. Ikramov; A. M. Nazari. On the 2-norm distance from a~normal matrix to the set of matrices with a~multiple zero eigenvalue. Zapiski Nauchnykh Seminarov POMI, Computational methods and algorithms. Part XVIII, Tome 323 (2005), pp. 50-56. http://geodesic.mathdoc.fr/item/ZNSL_2005_323_a5/