<p>A linear bounded operator <i>T</i> on a complex Banach space <i>X</i> is said to be <i>power-regular</i> if the sequence <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43036_2025_442_Article_IEq1.gif" Format="GIF" Height="24" Rendition="HTML" Resolution="72" Type="Linedraw" Width="97" /> </InlineMediaObject> <EquationSource Format="TEX">\(\{\Vert T^n x\Vert ^{\frac{1}{n}}\}_{n=1}^{\infty }\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow> <mo stretchy="false">{</mo> <mo stretchy="false">‖</mo> </mrow> <msup> <mi>T</mi> <mi>n</mi> </msup> <mi>x</mi> <msubsup> <mrow> <msup> <mo stretchy="false">‖</mo> <mfrac> <mn>1</mn> <mi>n</mi> </mfrac> </msup> <mo stretchy="false">}</mo> </mrow> <mrow> <mi>n</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>∞</mi> </msubsup> </mrow> </math></EquationSource> </InlineEquation> is convergent for every <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43036_2025_442_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="49" /> </InlineMediaObject> <EquationSource Format="TEX">\(x\in X\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>x</mi> <mo>∈</mo> <mi>X</mi> </mrow> </math></EquationSource> </InlineEquation>. For unilateral weighted shift <i>S</i>, we give a sufficient condition that <i>S</i> is power-regular. As an application, we construct a class of power-regular operators. Moreover, we show that there exist invertible power-regular bilateral weighted shifts, whose inverses are not power-regular.</p>

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Power-regularity of weighted shift operators

  • Chaolong Hu,
  • Youqing Ji

摘要

A linear bounded operator T on a complex Banach space X is said to be power-regular if the sequence \(\{\Vert T^n x\Vert ^{\frac{1}{n}}\}_{n=1}^{\infty }\) { T n x 1 n } n = 1 is convergent for every \(x\in X\) x X . For unilateral weighted shift S, we give a sufficient condition that S is power-regular. As an application, we construct a class of power-regular operators. Moreover, we show that there exist invertible power-regular bilateral weighted shifts, whose inverses are not power-regular.