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JOURNALS // Zapiski Nauchnykh Seminarov POMI // Archive

Zap. Nauchn. Sem. POMI, 2011 Volume 395, Pages 67–70 (Mi znsl4723)

Products of orthoprojectors and Hermitian matrices

Kh. D. Ikramov

Moscow State University, Moscow, Russia

Abstract: A proof of the following result is presented: A matrix $A\in M_n(\mathbf C)$ can be represented as a product $A=PH$, where $P$ is an orthoprojector and $H$ is Hermitian, if and only if $A$ satisfies the equation $A^{*2}A=A^*A^2$ (the Radjavi–Williams theorem). Unlike the original proof, ours makes no use of the Crimmins theorem.

Key words and phrases: Hermitian matrices, orthoprojector, image of a matrix.

UDC: 512.64

Received: 25.05.2011


 English version:
Journal of Mathematical Sciences (New York), 2012, 182:6, 782–784

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© Steklov Math. Inst. of RAS, 2024