An extension of Petek-Šemrl preserver theorems for Jordan embeddings of structural matrix algebras

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Auteurs principaux: Gogić, Ilja, Tomašević, Mateo
Format: Preprint
Publié: 2024
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author Gogić, Ilja
Tomašević, Mateo
author_facet Gogić, Ilja
Tomašević, Mateo
contents Let $M_n$ be the algebra of $n \times n$ complex matrices and $\mathcal{T}_n \subseteq M_n$ the corresponding upper-triangular subalgebra. In their influential work, Petek and Šemrl characterize Jordan automorphisms of $M_n$ and $\mathcal{T}_n$, when $n \geq 3$, as (injective in the case of $\mathcal{T}_n$) continuous commutativity and spectrum preserving maps $ϕ: M_n \to M_n$ and $ϕ: \mathcal{T}_n \to \mathcal{T}_n$. Recently, in a joint work with Petek, the authors extended this characterization to the maps $ϕ: \mathcal{A} \to M_n$, where $\mathcal{A}$ is an arbitrary subalgebra of $M_n$ that contains $\mathcal{T}_n$. In particular, any such map $ϕ$ is a Jordan embedding and hence of the form $ϕ(X)=TXT^{-1}$ or $ϕ(X)=TX^tT^{-1}$, for some invertible matrix $T\in M_n$. In this paper we further extend the aforementioned results in the context of structural matrix algebras (SMAs), i.e. subalgebras $\mathcal{A}$ of $M_n$ that contain all diagonal matrices. More precisely, we provide both a necessary and sufficient condition for an SMA $\mathcal{A}\subseteq M_n$ such that any injective continuous commutativity and spectrum preserving map $ϕ: \mathcal{A} \to M_n$ is necessarily a Jordan embedding. In contrast to the previous cases, such maps $ϕ$ no longer need to be multiplicative/antimultiplicative, nor rank-one preservers.
format Preprint
id arxiv_https___arxiv_org_abs_2411_11092
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle An extension of Petek-Šemrl preserver theorems for Jordan embeddings of structural matrix algebras
Gogić, Ilja
Tomašević, Mateo
Rings and Algebras
47B49, 15A27, 16S50, 16W20
Let $M_n$ be the algebra of $n \times n$ complex matrices and $\mathcal{T}_n \subseteq M_n$ the corresponding upper-triangular subalgebra. In their influential work, Petek and Šemrl characterize Jordan automorphisms of $M_n$ and $\mathcal{T}_n$, when $n \geq 3$, as (injective in the case of $\mathcal{T}_n$) continuous commutativity and spectrum preserving maps $ϕ: M_n \to M_n$ and $ϕ: \mathcal{T}_n \to \mathcal{T}_n$. Recently, in a joint work with Petek, the authors extended this characterization to the maps $ϕ: \mathcal{A} \to M_n$, where $\mathcal{A}$ is an arbitrary subalgebra of $M_n$ that contains $\mathcal{T}_n$. In particular, any such map $ϕ$ is a Jordan embedding and hence of the form $ϕ(X)=TXT^{-1}$ or $ϕ(X)=TX^tT^{-1}$, for some invertible matrix $T\in M_n$. In this paper we further extend the aforementioned results in the context of structural matrix algebras (SMAs), i.e. subalgebras $\mathcal{A}$ of $M_n$ that contain all diagonal matrices. More precisely, we provide both a necessary and sufficient condition for an SMA $\mathcal{A}\subseteq M_n$ such that any injective continuous commutativity and spectrum preserving map $ϕ: \mathcal{A} \to M_n$ is necessarily a Jordan embedding. In contrast to the previous cases, such maps $ϕ$ no longer need to be multiplicative/antimultiplicative, nor rank-one preservers.
title An extension of Petek-Šemrl preserver theorems for Jordan embeddings of structural matrix algebras
topic Rings and Algebras
47B49, 15A27, 16S50, 16W20
url https://arxiv.org/abs/2411.11092