<p>Let <i>α</i> &gt; 0 and let <i>μ</i> be a positive Borel measure on the interval [0,1). The Hankel matrix <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\({\cal{H}}_{\mu,\alpha}=(\mu_{n,k,\alpha})_{n,k\ge0}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msub> <mrow> <mrow> <mi mathvariant="script">H</mi> </mrow> </mrow> <mrow> <mi>μ</mi> <mo>,</mo> <mi>α</mi> </mrow> </msub> <mo>=</mo> <mo stretchy="false">(</mo> <msub> <mi>μ</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> <mo>,</mo> <mi>α</mi> </mrow> </msub> <msub> <mo stretchy="false">)</mo> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> <mo>≥</mo> <mn>0</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> with entries</p><p><Equation ID="Equa"> <EquationSource Format="TEX">\(\mu_{n,k,\alpha}=\int_{[0,1)}^{}{{\Gamma (n + \alpha)} \over {\Gamma (n + 1)\Gamma (\alpha)}}t^{n+k}{\rm d}\mu(t)\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msub> <mi>μ</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> <mo>,</mo> <mi>α</mi> </mrow> </msub> <mo>=</mo> <msubsup> <mo>∫</mo> <mrow> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> <mrow> <mtext>©</mtext> </mrow> </msubsup> <mrow> <mfrac> <mrow> <mi mathvariant="normal">Γ</mi> <mo stretchy="false">(</mo> <mi>n</mi> <mo>+</mo> <mi>α</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mi mathvariant="normal">Γ</mi> <mo stretchy="false">(</mo> <mi>n</mi> <mo>+</mo> <mn>1</mn> <mo stretchy="false">)</mo> <mi mathvariant="normal">Γ</mi> <mo stretchy="false">(</mo> <mi>α</mi> <mo stretchy="false">)</mo> </mrow> </mfrac> </mrow> <msup> <mi>t</mi> <mrow> <mi>n</mi> <mo>+</mo> <mi>k</mi> </mrow> </msup> <mrow> <mi mathvariant="normal">d</mi> </mrow> <mi>μ</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> </math></EquationSource> </Equation></p><p>induces, formally, the generalized-Hilbert operator</p><p><Equation ID="Equb"> <EquationSource Format="TEX">\({\cal{H}}_{\mu,\alpha}\left (f \right) \left (z \right) =\sum_{n=0}^{\infty} \left (\sum_{k=0}^{\infty} \mu_{n,k,\alpha}a_k \right)z^n,z\in\mathbb{D},\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msub> <mrow> <mrow> <mi mathvariant="script">H</mi> </mrow> </mrow> <mrow> <mi>μ</mi> <mo>,</mo> <mi>α</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>f</mi> <mo>)</mo> </mrow> <mrow> <mo>(</mo> <mi>z</mi> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mo>∑</mo> <mrow> <mi>n</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi mathvariant="normal">∞</mi> </mrow> </munderover> <mrow> <mo>(</mo> <munderover> <mo>∑</mo> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi mathvariant="normal">∞</mi> </mrow> </munderover> <msub> <mi>μ</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> <mo>,</mo> <mi>α</mi> </mrow> </msub> <msub> <mi>a</mi> <mi>k</mi> </msub> <mo>)</mo> </mrow> <msup> <mi>z</mi> <mi>n</mi> </msup> <mo>,</mo> <mi>z</mi> <mo>∈</mo> <mrow> <mi mathvariant="double-struck">D</mi> </mrow> <mo>,</mo> </math></EquationSource> </Equation></p><p>where <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(f(z)=\sum\nolimits_{k=0}^{\infty} a_kz^k\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi>f</mi> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> <mo>=</mo> <msubsup> <mo movablelimits="false">∑</mo> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi mathvariant="normal">∞</mi> </mrow> </msubsup> <msub> <mi>a</mi> <mi>k</mi> </msub> <msup> <mi>z</mi> <mi>k</mi> </msup> </math></EquationSource> </InlineEquation> is an analytic function in <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\mathbb{D}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="double-struck">D</mi> </mrow> </math></EquationSource> </InlineEquation>. This article is devoted to study the measures <i>μ</i> for which <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\({\cal{H}}_{\mu,\alpha}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msub> <mrow> <mrow> <mi mathvariant="script">H</mi> </mrow> </mrow> <mrow> <mi>μ</mi> <mo>,</mo> <mi>α</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> is a bounded (resp., compact) operator from <i>H</i><sup><i>p</i></sup>(0 &lt; <i>p</i> ≤ 1) into <i>H</i><sup><i>p</i></sup>(1 ≤ <i>q</i> &lt; ∞). We also study the analogous problem in the Hardy spaces <i>H</i><sup><i>p</i></sup>(1 ≤ <i>p</i> ≤ 2). Finally, we obtain the essential norm of <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\({\cal{H}}_{\mu,\alpha}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msub> <mrow> <mrow> <mi mathvariant="script">H</mi> </mrow> </mrow> <mrow> <mi>μ</mi> <mo>,</mo> <mi>α</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> from <i>H</i><sup><i>p</i></sup>(0 &lt; <i>p</i> ≤ 1) into <i>H</i><sup><i>p</i></sup>(1 ≤ <i>q</i> &lt; ∞).</p>

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A generalized Hilbert operator acting on Hardy spaces

  • Huiling Chen,
  • Shanli Ye

摘要

Let α > 0 and let μ be a positive Borel measure on the interval [0,1). The Hankel matrix \({\cal{H}}_{\mu,\alpha}=(\mu_{n,k,\alpha})_{n,k\ge0}\) H μ , α = ( μ n , k , α ) n , k 0 with entries

\(\mu_{n,k,\alpha}=\int_{[0,1)}^{}{{\Gamma (n + \alpha)} \over {\Gamma (n + 1)\Gamma (\alpha)}}t^{n+k}{\rm d}\mu(t)\) μ n , k , α = [ 0 , 1 ) © Γ ( n + α ) Γ ( n + 1 ) Γ ( α ) t n + k d μ ( t )

induces, formally, the generalized-Hilbert operator

\({\cal{H}}_{\mu,\alpha}\left (f \right) \left (z \right) =\sum_{n=0}^{\infty} \left (\sum_{k=0}^{\infty} \mu_{n,k,\alpha}a_k \right)z^n,z\in\mathbb{D},\) H μ , α ( f ) ( z ) = n = 0 ( k = 0 μ n , k , α a k ) z n , z D ,

where \(f(z)=\sum\nolimits_{k=0}^{\infty} a_kz^k\) f ( z ) = k = 0 a k z k is an analytic function in \(\mathbb{D}\) D . This article is devoted to study the measures μ for which \({\cal{H}}_{\mu,\alpha}\) H μ , α is a bounded (resp., compact) operator from Hp(0 < p ≤ 1) into Hp(1 ≤ q < ∞). We also study the analogous problem in the Hardy spaces Hp(1 ≤ p ≤ 2). Finally, we obtain the essential norm of \({\cal{H}}_{\mu,\alpha}\) H μ , α from Hp(0 < p ≤ 1) into Hp(1 ≤ q < ∞).