<p>We introduce and study a class of Toeplitz operators on the Dirichlet space <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathcal {D}_0}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">D</mi> <mn>0</mn> </msub> </math></EquationSource> </InlineEquation> induced by the symbol class <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="47" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal T({\mathcal {D}_0})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="script">T</mi> <mo stretchy="false">(</mo> <msub> <mi mathvariant="script">D</mi> <mn>0</mn> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> defined by <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq3.gif" Format="GIF" Height="54" Rendition="HTML" Resolution="72" Type="Linedraw" Width="485" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathcal {T}}({\mathcal {D}_0}) = \Bigg \{\psi \in h^{\infty }({\mathbb {D}}) : \left|\frac{\partial \psi }{ \partial z} \right|^{2} dA \text{ is } \text{ a } \text{ Carleson } \text{ measure } \text{ for }\,\, {\mathcal {D}}_0\Bigg \}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="script">T</mi> <mrow> <mo stretchy="false">(</mo> <msub> <mi mathvariant="script">D</mi> <mn>0</mn> </msub> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mrow> <mo maxsize="2.470em" minsize="2.470em" stretchy="true">{</mo> </mrow> <mi>ψ</mi> <mo>∈</mo> <msup> <mi>h</mi> <mi>∞</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="double-struck">D</mi> <mo stretchy="false">)</mo> </mrow> <mo>:</mo> <msup> <mfenced close="|" open="|"> <mfrac> <mrow> <mi>∂</mi> <mi>ψ</mi> </mrow> <mrow> <mi>∂</mi> <mi>z</mi> </mrow> </mfrac> </mfenced> <mn>2</mn> </msup> <mi>d</mi> <mi>A</mi> <mspace width="0.333333em" /> <mtext>is</mtext> <mspace width="0.333333em" /> <mspace width="0.333333em" /> <mtext>a</mtext> <mspace width="0.333333em" /> <mspace width="0.333333em" /> <mtext>Carleson</mtext> <mspace width="0.333333em" /> <mspace width="0.333333em" /> <mtext>measure</mtext> <mspace width="0.333333em" /> <mspace width="0.333333em" /> <mtext>for</mtext> <mspace width="0.333333em" /> <mspace width="0.166667em" /> <mspace width="0.166667em" /> <msub> <mi mathvariant="script">D</mi> <mn>0</mn> </msub> <mrow> <mo maxsize="2.470em" minsize="2.470em" stretchy="true">}</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, where <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="47" /> </InlineMediaObject> <EquationSource Format="TEX">\(h^{\infty }({\mathbb {D}})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>h</mi> <mi>∞</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="double-struck">D</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> denotes the set of all bounded harmonic functions on <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq5.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathbb {D}}.\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="double-struck">D</mi> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation> We find that this class of Toeplitz operators corresponds to the set of all bounded operators on the Dirichlet space <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathcal {D}_0}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">D</mi> <mn>0</mn> </msub> </math></EquationSource> </InlineEquation> represented by the Toeplitz matrices. We characterize the Toeplitz operators on the Dirichlet space <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathcal {D}_0}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">D</mi> <mn>0</mn> </msub> </math></EquationSource> </InlineEquation> by the Brown-Halmos type operator identity <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq8.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="87" /> </InlineMediaObject> <EquationSource Format="TEX">\(T_{\bar{z}}AT_z=A,\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>T</mi> <mover accent="true"> <mrow> <mi>z</mi> </mrow> <mrow> <mo stretchy="false">¯</mo> </mrow> </mover> </msub> <mi>A</mi> <msub> <mi>T</mi> <mi>z</mi> </msub> <mo>=</mo> <mi>A</mi> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> where <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq9.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="42" /> </InlineMediaObject> <EquationSource Format="TEX">\(T_z, T_{\bar{z}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>T</mi> <mi>z</mi> </msub> <mo>,</mo> <msub> <mi>T</mi> <mover accent="true"> <mrow> <mi>z</mi> </mrow> <mrow> <mo stretchy="false">¯</mo> </mrow> </mover> </msub> </mrow> </math></EquationSource> </InlineEquation> are the Toeplitz operators induced by the function <i>z</i> and <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq10.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="11" /> </InlineMediaObject> <EquationSource Format="TEX">\(\bar{z}\)</EquationSource> <EquationSource Format="MATHML"><math> <mover accent="true"> <mrow> <mi>z</mi> </mrow> <mrow> <mo stretchy="false">¯</mo> </mrow> </mover> </math></EquationSource> </InlineEquation> on the unit circle <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43037_2025_434_Article_IEq11.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="12" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathbb {T}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="double-struck">T</mi> </math></EquationSource> </InlineEquation>, respectively.</p>

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Toeplitz operators on the Dirichlet space and the Brown Halmos operator identity

  • Ashish Kujur,
  • Md. Ramiz Reza

摘要

We introduce and study a class of Toeplitz operators on the Dirichlet space \({\mathcal {D}_0}\) D 0 induced by the symbol class \(\mathcal T({\mathcal {D}_0})\) T ( D 0 ) defined by \({\mathcal {T}}({\mathcal {D}_0}) = \Bigg \{\psi \in h^{\infty }({\mathbb {D}}) : \left|\frac{\partial \psi }{ \partial z} \right|^{2} dA \text{ is } \text{ a } \text{ Carleson } \text{ measure } \text{ for }\,\, {\mathcal {D}}_0\Bigg \}\) T ( D 0 ) = { ψ h ( D ) : ψ z 2 d A is a Carleson measure for D 0 } , where \(h^{\infty }({\mathbb {D}})\) h ( D ) denotes the set of all bounded harmonic functions on \({\mathbb {D}}.\) D . We find that this class of Toeplitz operators corresponds to the set of all bounded operators on the Dirichlet space \({\mathcal {D}_0}\) D 0 represented by the Toeplitz matrices. We characterize the Toeplitz operators on the Dirichlet space \({\mathcal {D}_0}\) D 0 by the Brown-Halmos type operator identity \(T_{\bar{z}}AT_z=A,\) T z ¯ A T z = A , where \(T_z, T_{\bar{z}}\) T z , T z ¯ are the Toeplitz operators induced by the function z and \(\bar{z}\) z ¯ on the unit circle \({\mathbb {T}}\) T , respectively.