<p>If <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="57" /> </InlineMediaObject> <EquationSource Format="TEX">\(\alpha &gt;-1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>α</mi> <mo>&gt;</mo> <mo>-</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> the space of Dirichlet type <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq2.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="24" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {D}^2_\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mrow> <mi mathvariant="script">D</mi> </mrow> <mi>α</mi> <mn>2</mn> </msubsup> </math></EquationSource> </InlineEquation> consists of those functions <i>f</i> which are analytic in the unit disc <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq3.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathbb {D}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="double-struck">D</mi> </math></EquationSource> </InlineEquation> such that <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq4.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(f^\prime \)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>f</mi> <mo>′</mo> </msup> </math></EquationSource> </InlineEquation> belongs to the weighted Bergman space <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq5.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(A^2_\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>A</mi> <mi>α</mi> <mn>2</mn> </msubsup> </math></EquationSource> </InlineEquation>. The space <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq6.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">\(D^2_0\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>D</mi> <mn>0</mn> <mn>2</mn> </msubsup> </math></EquationSource> </InlineEquation> is the classical Dirichlet space <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq7.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {D}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">D</mi> </math></EquationSource> </InlineEquation>. If <i>g</i> is an analytic function in <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq8.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathbb D}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="double-struck">D</mi> </math></EquationSource> </InlineEquation>, we study the generalized Hilbert operator <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq9.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {H}_{g}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">H</mi> <mi>g</mi> </msub> </math></EquationSource> </InlineEquation> defined by <Equation ID="Equ30"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_Equ30.gif" Format="GIF" Height="44" Rendition="HTML" Resolution="72" Type="Linedraw" Width="202" /> </MediaObject> <EquationSource Format="TEX">\(\begin{aligned} \mathcal {H}_g(f)(z)=\int _0^1f(t)g'(tz)\,dt \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <msub> <mi mathvariant="script">H</mi> <mi>g</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <msubsup> <mo>∫</mo> <mn>0</mn> <mn>1</mn> </msubsup> <mi>f</mi> <mrow> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> </mrow> <msup> <mi>g</mi> <mo>′</mo> </msup> <mrow> <mo stretchy="false">(</mo> <mi>t</mi> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> <mspace width="0.166667em" /> <mi>d</mi> <mi>t</mi> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>acting on the spaces <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq10.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="24" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {D}^2_\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mrow> <mi mathvariant="script">D</mi> </mrow> <mi>α</mi> <mn>2</mn> </msubsup> </math></EquationSource> </InlineEquation> (<InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq11.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="74" /> </InlineMediaObject> <EquationSource Format="TEX">\(0\le \alpha \le 1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>≤</mo> <mi>α</mi> <mo>≤</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>). We obtain a characterization of those <i>g</i> for which <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq12.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {H}_g\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">H</mi> <mi>g</mi> </msub> </math></EquationSource> </InlineEquation> is bounded, compact, or Hilbert-Schmidt on the Dirichlet space <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq13.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {D}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">D</mi> </math></EquationSource> </InlineEquation>. In addition to this, we use our results concerning the operators <InlineEquation ID="IEq14"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq14.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {H}_g\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">H</mi> <mi>g</mi> </msub> </math></EquationSource> </InlineEquation> to study certain Cesàro-type operators <InlineEquation ID="IEq15"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq15.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="26" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {C}_{(\eta )}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">C</mi> <mrow> <mo stretchy="false">(</mo> <mi>η</mi> <mo stretchy="false">)</mo> </mrow> </msub> </math></EquationSource> </InlineEquation> acting on the spaces <InlineEquation ID="IEq16"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq16.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="24" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {D}^2_\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mrow> <mi mathvariant="script">D</mi> </mrow> <mi>α</mi> <mn>2</mn> </msubsup> </math></EquationSource> </InlineEquation> (<InlineEquation ID="IEq17"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq17.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="74" /> </InlineMediaObject> <EquationSource Format="TEX">\(0\le \alpha \le 1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>≤</mo> <mi>α</mi> <mo>≤</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>). We give also a characterization of the positive finite Borel measures <InlineEquation ID="IEq18"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq18.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mu \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>μ</mi> </math></EquationSource> </InlineEquation> in [0,&#xa0;1) for which a certain Cesàro type operator <InlineEquation ID="IEq19"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq19.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {C}_\mu \)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">C</mi> <mi>μ</mi> </msub> </math></EquationSource> </InlineEquation> associated to <InlineEquation ID="IEq20"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq20.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mu \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>μ</mi> </math></EquationSource> </InlineEquation> is bounded on the Bergman space <InlineEquation ID="IEq21"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq21.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(A^1_\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>A</mi> <mi>α</mi> <mn>1</mn> </msubsup> </math></EquationSource> </InlineEquation> (<InlineEquation ID="IEq22"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq22.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="57" /> </InlineMediaObject> <EquationSource Format="TEX">\(\alpha &gt;-1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>α</mi> <mo>&gt;</mo> <mo>-</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>). This is an extension of the previously known results for the spaces <InlineEquation ID="IEq23"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq23.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(A^p_\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>A</mi> <mi>α</mi> <mi>p</mi> </msubsup> </math></EquationSource> </InlineEquation> with <InlineEquation ID="IEq24"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq24.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="42" /> </InlineMediaObject> <EquationSource Format="TEX">\(p&gt;1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>&gt;</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq25"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13398_2025_1701_Article_IEq25.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="57" /> </InlineMediaObject> <EquationSource Format="TEX">\(\alpha &gt;-1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>α</mi> <mo>&gt;</mo> <mo>-</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>.</p>

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Operators of Hilbert and Cesàro type acting on Dirichlet spaces

  • Petros Galanopoulos,
  • Daniel Girela

摘要

If \(\alpha >-1\) α > - 1 the space of Dirichlet type \(\mathcal {D}^2_\alpha \) D α 2 consists of those functions f which are analytic in the unit disc \(\mathbb {D}\) D such that \(f^\prime \) f belongs to the weighted Bergman space \(A^2_\alpha \) A α 2 . The space \(D^2_0\) D 0 2 is the classical Dirichlet space \(\mathcal {D}\) D . If g is an analytic function in \({\mathbb D}\) D , we study the generalized Hilbert operator \(\mathcal {H}_{g}\) H g defined by \(\begin{aligned} \mathcal {H}_g(f)(z)=\int _0^1f(t)g'(tz)\,dt \end{aligned}\) H g ( f ) ( z ) = 0 1 f ( t ) g ( t z ) d t acting on the spaces \(\mathcal {D}^2_\alpha \) D α 2 ( \(0\le \alpha \le 1\) 0 α 1 ). We obtain a characterization of those g for which \(\mathcal {H}_g\) H g is bounded, compact, or Hilbert-Schmidt on the Dirichlet space \(\mathcal {D}\) D . In addition to this, we use our results concerning the operators \(\mathcal {H}_g\) H g to study certain Cesàro-type operators \(\mathcal {C}_{(\eta )}\) C ( η ) acting on the spaces \(\mathcal {D}^2_\alpha \) D α 2 ( \(0\le \alpha \le 1\) 0 α 1 ). We give also a characterization of the positive finite Borel measures \(\mu \) μ in [0, 1) for which a certain Cesàro type operator \(\mathcal {C}_\mu \) C μ associated to \(\mu \) μ is bounded on the Bergman space \(A^1_\alpha \) A α 1 ( \(\alpha >-1\) α > - 1 ). This is an extension of the previously known results for the spaces \(A^p_\alpha \) A α p with \(p>1\) p > 1 and \(\alpha >-1\) α > - 1 .