Characterizations of the semi-harmonious and harmonious quasi-projection pairs on Hilbert $C^*$-modules

Fuente: arXiv
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Auteurs principaux: Tian, Xiaoyi, Xu, Qingxiang, Fu, Chunhong
Format: Preprint
Publié: 2025
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author Tian, Xiaoyi
Xu, Qingxiang
Fu, Chunhong
author_facet Tian, Xiaoyi
Xu, Qingxiang
Fu, Chunhong
contents For each adjointable idempotent $Q$ on a Hilbert $C^*$-module $H$, a specific projection $m(Q)$ called the matched projection of $Q$ was introduced recently due to the characterization of the minimum value among all the distances from projections to $Q$. Inspired by the relationship between $m(Q)$ and $Q$, another term called the quasi-projection pair $(P,Q)$ was also introduced recently, where $P$ is a projection on $H$ satisfying $Q^*=(2P-I)Q(2P-I)$, in which $Q^*$ is the adjoint operator of the idempotent $Q$ and $I$ is the identity operator on $H$. This paper aims to make systematical characterizations of the semi-harmonious and harmonious quasi-projection pairs on Hilbert $C^*$-modules, and meanwhile to provide examples illustrating the non-triviality of the associated characterizations.
format Preprint
id arxiv_https___arxiv_org_abs_2502_20062
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Characterizations of the semi-harmonious and harmonious quasi-projection pairs on Hilbert $C^*$-modules
Tian, Xiaoyi
Xu, Qingxiang
Fu, Chunhong
Operator Algebras
Functional Analysis
For each adjointable idempotent $Q$ on a Hilbert $C^*$-module $H$, a specific projection $m(Q)$ called the matched projection of $Q$ was introduced recently due to the characterization of the minimum value among all the distances from projections to $Q$. Inspired by the relationship between $m(Q)$ and $Q$, another term called the quasi-projection pair $(P,Q)$ was also introduced recently, where $P$ is a projection on $H$ satisfying $Q^*=(2P-I)Q(2P-I)$, in which $Q^*$ is the adjoint operator of the idempotent $Q$ and $I$ is the identity operator on $H$. This paper aims to make systematical characterizations of the semi-harmonious and harmonious quasi-projection pairs on Hilbert $C^*$-modules, and meanwhile to provide examples illustrating the non-triviality of the associated characterizations.
title Characterizations of the semi-harmonious and harmonious quasi-projection pairs on Hilbert $C^*$-modules
topic Operator Algebras
Functional Analysis
url https://arxiv.org/abs/2502.20062