A Family of Semi-norms in $C^*$-algebras

Fuente: arXiv
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Autores principales: Augustine, Athul, Bhunia, Pintu, Shankar, P.
Formato: Preprint
Publicado: 2025
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author Augustine, Athul
Bhunia, Pintu
Shankar, P.
author_facet Augustine, Athul
Bhunia, Pintu
Shankar, P.
contents We introduce a new family of non-negative real-valued functions on a $C^*$-algebra $\mathcal{A}$, i.e., for $0\leq μ\leq 1,$ $$\|a\|_{σ_μ}= \text{sup}\left\lbrace \sqrt{|f(a)|^2 σ_μ f(a^*a)}: f\in \mathcal{A}', \, f(1)=\|f\|=1 \right\rbrace, \quad $$ where $a\in \mathcal{A}$ and $σ_μ$ is an interpolation path of the symmetric mean $σ$. These functions are semi-norms as they satisfy the norm axioms, except for the triangle inequality. Special cases satisfying triangle inequality, and a complete equality characterization is also discussed. Various bounds and relationships will be established for this new family, with a connection to the existing literature in the algebra of all bounded linear operators on a Hilbert space.
format Preprint
id arxiv_https___arxiv_org_abs_2503_01331
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle A Family of Semi-norms in $C^*$-algebras
Augustine, Athul
Bhunia, Pintu
Shankar, P.
Functional Analysis
Operator Algebras
47A12, 47A30, 26E60, 46L05
We introduce a new family of non-negative real-valued functions on a $C^*$-algebra $\mathcal{A}$, i.e., for $0\leq μ\leq 1,$ $$\|a\|_{σ_μ}= \text{sup}\left\lbrace \sqrt{|f(a)|^2 σ_μ f(a^*a)}: f\in \mathcal{A}', \, f(1)=\|f\|=1 \right\rbrace, \quad $$ where $a\in \mathcal{A}$ and $σ_μ$ is an interpolation path of the symmetric mean $σ$. These functions are semi-norms as they satisfy the norm axioms, except for the triangle inequality. Special cases satisfying triangle inequality, and a complete equality characterization is also discussed. Various bounds and relationships will be established for this new family, with a connection to the existing literature in the algebra of all bounded linear operators on a Hilbert space.
title A Family of Semi-norms in $C^*$-algebras
topic Functional Analysis
Operator Algebras
47A12, 47A30, 26E60, 46L05
url https://arxiv.org/abs/2503.01331