<p>Let <i>X</i> be a smooth complex projective variety equipped with an action of a linear algebraic group <i>G</i> over <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathbb {C}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="double-struck">C</mi> </math></EquationSource> </InlineEquation>. Let <i>D</i> be a reduced effective divisor on <i>X</i> that is invariant under the <i>G</i>–action on <i>X</i>. Let <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq2.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\(s_D\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>s</mi> <mi>D</mi> </msub> </math></EquationSource> </InlineEquation> be the canonical section of <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="53" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal {O}_X(D)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi mathvariant="script">O</mi> <mi>X</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>D</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> vanishing along <i>D</i>. Given a positive integer <i>r</i>, consider the stack <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq4.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="131" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathfrak {X}:= \mathfrak {X}_{(\mathcal {O}_X(D),\, s_D,\, r)}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="fraktur">X</mi> <mo>:</mo> <mo>=</mo> <msub> <mi mathvariant="fraktur">X</mi> <mrow> <mo stretchy="false">(</mo> <msub> <mi mathvariant="script">O</mi> <mi>X</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>D</mi> <mo stretchy="false">)</mo> </mrow> <mo>,</mo> <mspace width="0.166667em" /> <msub> <mi>s</mi> <mi>D</mi> </msub> <mo>,</mo> <mspace width="0.166667em" /> <mi>r</mi> <mo stretchy="false">)</mo> </mrow> </msub> </mrow> </math></EquationSource> </InlineEquation> of <i>r</i>-th roots of <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="65" /> </InlineMediaObject> <EquationSource Format="TEX">\((\mathcal {O}_X, s_D)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <msub> <mi mathvariant="script">O</mi> <mi>X</mi> </msub> <mo>,</mo> <msub> <mi>s</mi> <mi>D</mi> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> together with the natural morphism <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq6.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="82" /> </InlineMediaObject> <EquationSource Format="TEX">\(\pi : \mathfrak {X} \rightarrow X\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>π</mi> <mo>:</mo> <mi mathvariant="fraktur">X</mi> <mo stretchy="false">→</mo> <mi>X</mi> </mrow> </math></EquationSource> </InlineEquation>. Under the assumption that <i>G</i> has no non-trivial characters, we show that the <i>G</i>–action on <i>X</i> naturally lifts to a <i>G</i>–action on <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq7.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathfrak {X}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="fraktur">X</mi> </math></EquationSource> </InlineEquation> such that <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq8.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\pi \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>π</mi> </math></EquationSource> </InlineEquation> becomes <i>G</i>–equivariant, and the tautological invertible sheaf <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq9.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="29" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathscr {M}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">M</mi> </math></EquationSource> </InlineEquation> on <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq7.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathfrak {X}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="fraktur">X</mi> </math></EquationSource> </InlineEquation> admits a linearization of this <i>G</i>–action. Finally, we define the notions of <i>G</i>–equivariant logarithmic connections on <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq7.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathfrak {X}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="fraktur">X</mi> </math></EquationSource> </InlineEquation> and <i>G</i>–equivariant parabolic connections on <i>X</i> with rational parabolic weights along <i>D</i>, and establish an equivalence between the category of <i>G</i>–equivariant logarithmic connections on <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10711_2025_1022_Article_IEq7.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathfrak {X}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="fraktur">X</mi> </math></EquationSource> </InlineEquation> and the category of <i>G</i>–equivariant parabolic connections on <i>X</i> with rational parabolic weights along <i>D</i>.</p>

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Equivariant Parabolic connections and stack of roots

  • Sujoy Chakraborty,
  • Arjun Paul

摘要

Let X be a smooth complex projective variety equipped with an action of a linear algebraic group G over \(\mathbb {C}\) C . Let D be a reduced effective divisor on X that is invariant under the G–action on X. Let \(s_D\) s D be the canonical section of \(\mathcal {O}_X(D)\) O X ( D ) vanishing along D. Given a positive integer r, consider the stack \(\mathfrak {X}:= \mathfrak {X}_{(\mathcal {O}_X(D),\, s_D,\, r)}\) X : = X ( O X ( D ) , s D , r ) of r-th roots of \((\mathcal {O}_X, s_D)\) ( O X , s D ) together with the natural morphism \(\pi : \mathfrak {X} \rightarrow X\) π : X X . Under the assumption that G has no non-trivial characters, we show that the G–action on X naturally lifts to a G–action on \(\mathfrak {X}\) X such that \(\pi \) π becomes G–equivariant, and the tautological invertible sheaf \(\mathscr {M}\) M on \(\mathfrak {X}\) X admits a linearization of this G–action. Finally, we define the notions of G–equivariant logarithmic connections on \(\mathfrak {X}\) X and G–equivariant parabolic connections on X with rational parabolic weights along D, and establish an equivalence between the category of G–equivariant logarithmic connections on \(\mathfrak {X}\) X and the category of G–equivariant parabolic connections on X with rational parabolic weights along D.