Abstract
Let $H:M_m\to M_m$ be a holomorphic function of the algebra $M_m$ of complex $m\times m$ matrices. Suppose that $H$ is orthogonally additive and orthogonally multiplicative on self-adjoint elements. We show that either the range of $H$ consists of zero trace elements, or there is a scalar sequence $\{\lambda_n\}$ and an invertible $S$ in $M_m$ such that $$ H(x) =\sum_{n\geq 1} \lambda_n S^{-1}x^nS, \quad\forall x \in M_m,%\eqno{(\ddag)}$$ or $$ H(x) =\sum_{n\geq 1} \lambda_n S^{-1}(x^t)^nS, \quad\forall x \in M_m. $$ Here, $x^t$ is the transpose of the matrix $x$. In the latter case, we always have the first representation form when $H$ also preserves zero products. We also discuss the cases where the domain and the range carry different dimensions.
Citation
Qingying Bu. Chingjou Liao. Ngai-Ching Wong. "Orthogonally additive and orthogonally multiplicative holomorphic functions of matrices." Ann. Funct. Anal. 5 (2) 80 - 89, 2014. https://doi.org/10.15352/afa/1396833505
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