• Title, Summary, Keyword: spherical isometry

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SUPERCYCLICITY OF ℓp-SPHERICAL AND TORAL ISOMETRIES ON BANACH SPACES

  • Ansari, Mohammad;Hedayatian, Karim;Khani-Robati, Bahram
    • Communications of the Korean Mathematical Society
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    • v.32 no.3
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    • pp.653-659
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    • 2017
  • Let $p{\geq}1$ be a real number. A tuple $T=(T_1,{\ldots},T_n)$ of commuting bounded linear operators on a Banach space X is called an ${\ell}^p$-spherical isometry if ${\sum_{i=1}^{n}}{\parallel}T_ix{\parallel}^p={\parallel}x{\parallel}^p$ for all $x{\in}X$. The tuple T is called a toral isometry if each Ti is an isometry. By a result of Ansari, Hedayatian, Khani-Robati and Moradi, for every $n{\geq}1$, there is a supercyclic ${\ell}^2$-spherical isometric n-tuple on ${\mathbb{C}}^n$ but there is no supercyclic ${\ell}^2$-spherical isometry on an infinite-dimensional Hilbert space. In this article, we investigate the supercyclicity of ${\ell}^p$-spherical isometries and toral isometries on Banach spaces. Also, we introduce the notion of semicommutative tuples and we show that the Banach spaces ${\ell}^p$ ($1{\leq}p$ < ${\infty}$) support supercyclic ${\ell}^p$-spherical isometric semi-commutative tuples. As a result, all separable infinite-dimensional complex Hilbert spaces support supercyclic spherical isometric semi-commutative tuples.

SUPERCYCLICITY OF JOINT ISOMETRIES

  • ANSARI, MOHAMMAD;HEDAYATIAN, KARIM;KHANI-ROBATI, BAHRAM;MORADI, ABBAS
    • Bulletin of the Korean Mathematical Society
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    • v.52 no.5
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    • pp.1481-1487
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    • 2015
  • Let H be a separable complex Hilbert space. A commuting tuple $T=(T_1,{\cdots},T_n)$ of bounded linear operators on H is called a spherical isometry if $\sum_{i=1}^{n}T^*_iT_i=I$. The tuple T is called a toral isometry if each $T_i$ is an isometry. In this paper, we show that for each $n{\geq}1$ there is a supercyclic n-tuple of spherical isometries on $\mathbb{C}^n$ and there is no spherical or toral isometric tuple of operators on an infinite-dimensional Hilbert space.