• Title, Summary, Keyword: algebraic spectral subspace

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ALGEBRAIC SPECTRAL SUBSPACES OF OPERATORS WITH FINITE ASCENT

  • Han, Hyuk
    • Journal of the Chungcheong Mathematical Society
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    • v.29 no.4
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    • pp.677-686
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    • 2016
  • Algebraic spectral subspaces were introduced by Johnson and Sinclair via a transnite sequence of spaces. Laursen simplified the definition of algebraic spectral subspace. Algebraic spectral subspaces are useful in automatic continuity theory of intertwining linear operators on Banach spaces. In this paper, we characterize algebraic spectral subspaces of operators with finite ascent. From this characterization we show that if T is a generalized scalar operator, then T has finite ascent.

ON PREHERMITIAN OPERATORS

  • YOO JONG-KWANG;HAN HYUK
    • Communications of the Korean Mathematical Society
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    • v.21 no.1
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    • pp.53-64
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    • 2006
  • In this paper, we are concerned with the algebraic representation of the quasi-nilpotent part for prehermitian operators on Banach spaces. The quasi-nilpotent part of an operator plays a significant role in the spectral theory and Fredholm theory of operators on Banach spaces. Properties of the quasi-nilpotent part are investigated and an application is given to totally paranormal and prehermitian operators.

SOME INVARIANT SUBSPACES FOR SUBSCALAR OPERATORS

  • Yoo, Jong-Kwang
    • Bulletin of the Korean Mathematical Society
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    • v.48 no.6
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    • pp.1129-1135
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    • 2011
  • In this note, we prove that every subscalar operator with finite spectrum is algebraic. In particular, a quasi-nilpotent subscala operator is nilpotent. We also prove that every subscalar operator with property (${\delta}$) on a Banach space of dimension greater than 1 has a nontrivial invariant closed linear subspace.

SPECTRA OF ASYMPTOTICALLY QUASISIMILAR SUBDECOMPOSABLE OPERATORS

  • Yoo, Jong-Kwang;Han, Hyuk
    • Journal of the Chungcheong Mathematical Society
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    • v.22 no.2
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    • pp.271-279
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    • 2009
  • In this paper, we prove that asymptotically quasisimilar sub-decomposable operators have equal spectra and quasisimilar decomposable operators have equal spectra. Moreover, every subscalar operator is admissible.

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ON SPECTRAL SUBSPACES OF SEMI-SHIFTS

  • Han, Hyuk;Yoo, Jong-Kwang
    • Journal of the Chungcheong Mathematical Society
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    • v.21 no.2
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    • pp.247-257
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    • 2008
  • In this paper, we show that for a semi-shift the analytic spectral subspace coincides with the algebraic spectral subspace. Using this result, we have the following result. Let T be a decomposable operator on a Banach space ${\mathcal{X}}$ and let S be a semi-shift on a Banach space ${\mathcal{Y}}$. Then every linear operator ${\theta}:{\mathcal{X}}{\rightarrow}{\mathcal{Y}}$ with $S{\theta}={\theta}T$ is necessarily continuous.

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LOCAL SPECTRAL PROPERTIES OF SEMI-SHIFTS

  • Yoo, Jong-Kwang;Kim, Yong-Il
    • Journal of applied mathematics & informatics
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    • v.28 no.1_2
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    • pp.499-507
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    • 2010
  • In this note, we study the local spectral properties of semi-shifts. If $T\;{\in}\;L(X)$ is a semi-shift on a complex Banach space X, then T is admissible. We also prove that if $T\;{\in}\;L(X)$ is subadmissible, then $X_T(F)\;=\;E_T(F)$ for all closed $F\;{\subseteq}\;\mathbb{C}$. In particular, every subscalar operator on a Banach space is admissible.

CONTINUITY OF LINEAR OPERATOR INTERTWINING WITH DECOMPOSABLE OPERATORS AND PURE HYPONORMAL OPERATORS

  • Park, Sung-Wook;Han, Hyuk;Park, Se Won
    • Journal of the Chungcheong Mathematical Society
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    • v.16 no.1
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    • pp.37-48
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    • 2003
  • In this paper, we show that for a pure hyponormal operator the analytic spectral subspace and the algebraic spectral subspace are coincide. Using this result, we have the following result: Let T be a decomposable operator on a Banach space X and let S be a pure hyponormal operator on a Hilbert space H. Then every linear operator ${\theta}:X{\rightarrow}H$ with $S{\theta}={\theta}T$ is automatically continuous.

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SOME INVARIANT SUBSPACES FOR BOUNDED LINEAR OPERATORS

  • Yoo, Jong-Kwang
    • Journal of the Chungcheong Mathematical Society
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    • v.24 no.1
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    • pp.19-34
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    • 2011
  • A bounded linear operator T on a complex Banach space X is said to have property (I) provided that T has Bishop's property (${\beta}$) and there exists an integer p > 0 such that for a closed subset F of ${\mathbb{C}}$ ${X_T}(F)={E_T}(F)=\bigcap_{{\lambda}{\in}{\mathbb{C}}{\backslash}F}(T-{\lambda})^PX$ for all closed sets $F{\subseteq}{\mathbb{C}}$, where $X_T$(F) denote the analytic spectral subspace and $E_T$(F) denote the algebraic spectral subspace of T. Easy examples are provided by normal operators and hyponormal operators in Hilbert spaces, and more generally, generalized scalar operators and subscalar operators in Banach spaces. In this paper, we prove that if T has property (I), then the quasi-nilpotent part $H_0$(T) of T is given by $$KerT^P=\{x{\in}X:r_T(x)=0\}={\bigcap_{{\lambda}{\neq}0}(T-{\lambda})^PX$$ for all sufficiently large integers p, where ${r_T(x)}=lim\;sup_{n{\rightarrow}{\infty}}{\parallel}T^nx{\parallel}^{\frac{1}{n}}$. We also prove that if T has property (I) and the spectrum ${\sigma}$(T) is finite, then T is algebraic. Finally, we prove that if $T{\in}L$(X) has property (I) and has decomposition property (${\delta}$) then T has a non-trivial invariant closed linear subspace.