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Mohammad Reza Azimi

Mohammad Reza Azimi

Academic rank: Associate Professor
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Education: PhD.
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Research

Title
J-class sequences of linear operators
Type
JournalPaper
Keywords
Sequences of operators, Hypercyclic operators, $J$-class operators.
Year
2018
Journal Complex Analysis and Operator Theory
DOI
Researchers Mohammad Reza Azimi

Abstract

In this paper, we study the extended limit set $J_{\{T_n\}}(x)$ for a sequence of bounded linear operators $\{T_n\}_{n=1}^{\infty}$ on a separable Banach space $X$, to describe the dynamics of a sequence of linear operators. First, it is shown that a mutually commuting sequence $\{T_n\}_{n=1}^{\infty} \subseteq \mathcal{B}(X)$ is hypercyclic if and only if the closed and connected set $H=\{x\in X: J_{\{T_n\}}(x)=X\}$ is dense in $X$ or equivalently has nonempty interior. % Later, we show that a sequence % $\{T_n\}_{n=1}^{\infty}$ with $T_{m+n}=T_mT_n$ % is hypercyclic if and only if there exists a cyclic vector %$x\in X$ such that $J_{\{T_n\}}(x)=X$. Furthermore, for such a %sequence we prove that it is $J$-class if and only if %$J_{\{T_n\}}(0)=X$ or equivalently, $J_{\{T_n\}}(x)=X$ for some % nonzero periodic vector $x$. Later, we prove that a mutually commuting sequence $\{T_n\}_{n=1}^{\infty}$ with dense ranges, is hypercyclic if there exists a cyclic vector $x\in X$ for some term of $\{T_n\}_{n=1}^{\infty}$ such that $J_{\{T_n\}}(x)=X$. Furthermore, it is proved that an arbitrary sequence $\{T_n\}_{n=1}^{\infty}$ is $J$-class if and only if $J_{\{T_n\}}(0)=X$ or equivalently, $J_{\{T_n\}}(x)=X$ for some nonzero mixed periodic vector $x$. Finally, some examples are presented to illustrate these results.