$$G_{1}$$-class elements in a Banach algebra

نویسندگان

چکیده

Let A be a complex unital Banach algebra with unit 1. An element $$a\in A$$ is said to of $$G_{1}$$ -class if $$\begin{aligned} \Vert (z-a)^{-1}\Vert =\frac{1}{\text {d}(z,\sigma (a))} \quad \forall z\in {\mathbb {C}}\setminus \sigma (a). \end{aligned}$$ Here $$d(z, (a))$$ denotes the distance between z and spectrum $$\sigma (a)$$ a. Some examples such elements are given also some properties proved. It shown that $$G_1$$ scalar multiple 1 only its singleton set consisting scalar. proved T class operator on space X, then every isolated point (T)$$ an eigenvalue T. If, in addition, finite, X direct sum eigenspaces

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ژورنال

عنوان ژورنال: The journal of analysis

سال: 2022

ISSN: ['0971-3611']

DOI: https://doi.org/10.1007/s41478-022-00431-z