• 충청수학회지
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• 제27권1호
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• pp.99-103
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• 2014

In this paper, we characterize the m-isometric weighted shifts, using this characterization, we study the relations between the hyponormality and the m-isometricity of operators.

• 충청수학회지
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• 제31권3호
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• pp.325-331
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• 2018

In this paper, we study which transform preserves the k-hyponormality of weighted shifts. For this, we introduce a new transform, the modulus multiplication transform, and then examine various properties of it.

• 대한수학회보
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• 제48권3호
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• pp.647-653
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• 2011

In this note we are concerned with the hyponormality of Toeplitz operators $T_{\phi}$ with polynomial symbols ${\phi}=\bar{g}+f(f,g{\in}H^{\infty}(\mathbb{T}))$ when g divides f.

• 대한수학회지
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• 제42권2호
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• pp.387-403
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• 2005

In this note we consider the hyponormality of Toeplitz operators $B_\varphi$ on the Bergman space $L_a^2$ (D) with symbol in the class of functions f + g with polynomials f and g

• 대한수학회보
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• 제42권2호
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• pp.269-277
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• 2005

The tensor product $A{\bigotimes}B$ of Hilbert space operators A and B will be shown to be log-hyponormal if and only if A and Bare log-hyponormal. Some general comments about generalized hyponormality are also made.

• 대한수학회보
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• 제37권2호
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• pp.347-352
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• 2000

In this note we answer to a question of Curto: Non-first two equal weights in the weighted shift force subnormality in the presence of quadratic hyponormality. Also it is shown that every hyponormal weighted shift with two equal weights cannot be polynomially hyponormal without being flat.

• 호남수학학술지
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• 제39권1호
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• pp.83-91
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• 2017

In this note we consider weakly hyponormal weighted shift. In particular, we focus on the weak 4-hyponormality of the weighted shift with the Bergman tail. This is related to the open question of finding a polynomially hyponormal non-subnormal weighted shift.

• 대한수학회논문집
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• 제33권3호
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• pp.787-798
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• 2018

For $1{\leq}p{\leq}{\infty}$, let $H^p$ be the usual Hardy space on the unit circle. When ${\alpha}$ and ${\beta}$ are bounded functions, a singular integral operator $S_{{\alpha},{\beta}}$ is defined as the following: $S_{{\alpha},{\beta}}(f+{\bar{g}})={\alpha}f+{\beta}{\bar{g}}(f{\in}H^p,\;g{\in}zH^p)$. When p = 2, we study the hyponormality of $S_{{\alpha},{\beta}}$ when ${\alpha}$ and ${\beta}$ are some special functions.

• 호남수학학술지
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• 제40권1호
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• pp.155-162
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• 2018

In this paper, we are concerned with hyponormal Toeplitz operators on the Hardy space of the unit circle. Our main result of this paper is to provide a simple and transparent proof on the hyponormality of Toeplitz operators with symmetric-type symbols via Schur complement lemma.

• Kyungpook Mathematical Journal
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• 제49권4호
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• pp.683-689
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• 2009

We investigate the gaps among classes of weakly hyponormal composition operators induced by Embry characterization for the subnormality. The relationship between subnormality and weak hyponormality will be discussed in a version of composition operator induced by a non-singular measurable transformation.