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Unitary Tridiagonalisation in M(4, C)

Vishwambhar Pati
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Abstract

A question of interest in Linear Algebra is whether all n x n complex matrices can be unitarily tridiagonalised. The answer for all n not equal to 4 (affirmative or negative) has been known for a while, whereas the case n=4 seems to have remained open. In this paper, we settle the n=4 case in the affirmative. Some machinery from complex algebraic geometry needs to be used.

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Vishwambhar Pati. 2001-12-19. Unitary Tridiagonalisation in M(4, C). https://arxiv.org/abs/math/0109051

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