<p>Let <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3860_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="63" /> </InlineMediaObject> <EquationSource Format="TEX">\( (\Theta ,T,\mu ) \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="normal">Θ</mi> <mo>,</mo> <mi>T</mi> <mo>,</mo> <mi>μ</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> be an ergodic topological dynamical system. The fibered rotation number for cocycles in <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3860_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="92" /> </InlineMediaObject> <EquationSource Format="TEX">\( \Theta \times \textrm{SL}(2,{{\mathbb {R}}}) \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Θ</mi> <mo>×</mo> <mtext>SL</mtext> <mo stretchy="false">(</mo> <mn>2</mn> <mo>,</mo> <mi mathvariant="double-struck">R</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, acting on <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3860_Article_IEq3.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="62" /> </InlineMediaObject> <EquationSource Format="TEX">\( \Theta \times {{\mathbb {R}}}\mathbb {P}^1 \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Θ</mi> <mo>×</mo> <mi mathvariant="double-struck">R</mi> <msup> <mrow> <mi mathvariant="double-struck">P</mi> </mrow> <mn>1</mn> </msup> </mrow> </math></EquationSource> </InlineEquation> is well-defined and has wide applications in the study of the spectral theory of Schrödinger operators. In this paper, we will provide its natural generalization for higher dimensional cocycles in <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3860_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="109" /> </InlineMediaObject> <EquationSource Format="TEX">\( \Theta \times \textrm{Sp}(2\,m,{{\mathbb {R}}}) \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Θ</mi> <mo>×</mo> <mtext>Sp</mtext> <mo stretchy="false">(</mo> <mn>2</mn> <mspace width="0.166667em" /> <mi>m</mi> <mo>,</mo> <mi mathvariant="double-struck">R</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> or <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3860_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="121" /> </InlineMediaObject> <EquationSource Format="TEX">\( \Theta \times \textrm{HSp}(2\,m,\mathbb {C}) \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Θ</mi> <mo>×</mo> <mtext>HSp</mtext> <mo stretchy="false">(</mo> <mn>2</mn> <mspace width="0.166667em" /> <mi>m</mi> <mo>,</mo> <mi mathvariant="double-struck">C</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, where <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3860_Article_IEq6.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="72" /> </InlineMediaObject> <EquationSource Format="TEX">\( \textrm{Sp}(2m,{{\mathbb {R}}}) \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>Sp</mtext> <mo stretchy="false">(</mo> <mn>2</mn> <mi>m</mi> <mo>,</mo> <mi mathvariant="double-struck">R</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3860_Article_IEq7.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="85" /> </InlineMediaObject> <EquationSource Format="TEX">\( \textrm{HSp}(2m,\mathbb {C}) \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>HSp</mtext> <mo stretchy="false">(</mo> <mn>2</mn> <mi>m</mi> <mo>,</mo> <mi mathvariant="double-struck">C</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> respectively refer to the 2<i>m</i>-dimensional symplectic or Hermitian symplectic matrices. As a corollary, we establish the equivalence between the integrated density of states for generalized Schrödinger operators and the fibered rotation number; and the Gap Labelling Theorem via the Schwartzman group, as expected from the one dimensional case [<CitationRef CitationID="CR11">11</CitationRef>, <CitationRef CitationID="CR33">33</CitationRef>].</p>

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The fibered rotation number for ergodic symplectic cocycles and its applications: I. Gap labelling theorem

  • Xianzhe Li,
  • Li Wu

摘要

Let \( (\Theta ,T,\mu ) \) ( Θ , T , μ ) be an ergodic topological dynamical system. The fibered rotation number for cocycles in \( \Theta \times \textrm{SL}(2,{{\mathbb {R}}}) \) Θ × SL ( 2 , R ) , acting on \( \Theta \times {{\mathbb {R}}}\mathbb {P}^1 \) Θ × R P 1 is well-defined and has wide applications in the study of the spectral theory of Schrödinger operators. In this paper, we will provide its natural generalization for higher dimensional cocycles in \( \Theta \times \textrm{Sp}(2\,m,{{\mathbb {R}}}) \) Θ × Sp ( 2 m , R ) or \( \Theta \times \textrm{HSp}(2\,m,\mathbb {C}) \) Θ × HSp ( 2 m , C ) , where \( \textrm{Sp}(2m,{{\mathbb {R}}}) \) Sp ( 2 m , R ) and \( \textrm{HSp}(2m,\mathbb {C}) \) HSp ( 2 m , C ) respectively refer to the 2m-dimensional symplectic or Hermitian symplectic matrices. As a corollary, we establish the equivalence between the integrated density of states for generalized Schrödinger operators and the fibered rotation number; and the Gap Labelling Theorem via the Schwartzman group, as expected from the one dimensional case [11, 33].