<p>We consider the set <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12215_2025_1189_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="53" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathcal {U}}{\mathcal {T}}(A)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="script">U</mi> <mi mathvariant="script">T</mi> <mo stretchy="false">(</mo> <mi>A</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> consisting of all scalars <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12215_2025_1189_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\lambda \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>λ</mi> </math></EquationSource> </InlineEquation> for which operator <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12215_2025_1189_Article_IEq3.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="56" /> </InlineMediaObject> <EquationSource Format="TEX">\(A-\lambda I\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>A</mi> <mo>-</mo> <mi>λ</mi> <mi>I</mi> </mrow> </math></EquationSource> </InlineEquation> is universal in the sense of Gian-Carlo Rota. We determine <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12215_2025_1189_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="53" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathcal {U}}{\mathcal {T}}(A)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="script">U</mi> <mi mathvariant="script">T</mi> <mo stretchy="false">(</mo> <mi>A</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> in most cases when <i>A</i> is a composition operator on the usual Hardy space <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12215_2025_1189_Article_IEq5.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="23" /> </InlineMediaObject> <EquationSource Format="TEX">\(H^2\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>H</mi> <mn>2</mn> </msup> </math></EquationSource> </InlineEquation> induced by an inner map or the adjoint of that operator. The same problem is considered and solved for select, non-inner, analytic selfmaps of the unit disc and the composition operators induced by them.</p>

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Universal translates of composition operators and their adjoints

  • Valentin Matache

摘要

We consider the set \({\mathcal {U}}{\mathcal {T}}(A)\) U T ( A ) consisting of all scalars \(\lambda \) λ for which operator \(A-\lambda I\) A - λ I is universal in the sense of Gian-Carlo Rota. We determine \({\mathcal {U}}{\mathcal {T}}(A)\) U T ( A ) in most cases when A is a composition operator on the usual Hardy space \(H^2\) H 2 induced by an inner map or the adjoint of that operator. The same problem is considered and solved for select, non-inner, analytic selfmaps of the unit disc and the composition operators induced by them.