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arXiv 2101.04396math.FA
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Hilbert $C^*$ -模的数值半径

Numerical radius in Hilbert $C^*$-modules

Ali Zamani

摘要:

利用Hilbert $C^*$ -模$\big(\mathscr{V}, {\|\!\cdot\!\|}\big)$的连接代数,引入$Ω(x)$作为元素$x\in\mathscr{V}$的数值半径的定义,证明了$Ω(\cdot)$是$\mathscr{V}$上的范数,使得$\frac{1}{2}{\|x\|} \leq Ω(x) \leq {\|x\|}$ .此外,我们还得到了$Ω(x) = \frac{1}{2}{\|x\|}$的一个等价条件.此外,我们提出了一个改进的三角不等式的范数$Ω(\cdot)$。对其它相关结果也进行了讨论。

英文摘要:

Utilizing the linking algebra of a Hilbert $C^*$-module $\big(\mathscr{V}, {\|\!\cdot\!\|}\big)$, we introduce $Ω(x)$ as a definition of numerical radius for an element $x\in\mathscr{V}$ and then show that $Ω(\cdot)$ is a norm on $\mathscr{V}$ such that $\frac{1}{2}{\|x\|} \leq Ω(x) \leq {\|x\|}$. In addition, we obtain an equivalent condition for $Ω(x) = \frac{1}{2}{\|x\|}$. Moreover, we present a refinement of the triangle inequality for the norm $Ω(\cdot)$. Some other related results are also discussed.

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