<p>Let <i>C</i> be an affine curve over an algebraically closed field <i>k</i> of characteristic <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_817_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="42" /> </InlineMediaObject> <EquationSource Format="TEX">\(p&gt;0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>&gt;</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation>. Given an embedding problem <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_817_Article_IEq2.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="228" /> </InlineMediaObject> <EquationSource Format="TEX">\((\beta :\Gamma \longrightarrow G, \alpha : \pi ^{\acute{\textrm{e}}\textrm{t}}_1(C)\longrightarrow G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>β</mi> <mo>:</mo> <mi mathvariant="normal">Γ</mi> <mo stretchy="false">⟶</mo> <mi>G</mi> <mo>,</mo> <mi>α</mi> <mo>:</mo> <msubsup> <mi>π</mi> <mn>1</mn> <mrow> <mover accent="true"> <mtext>e</mtext> <mo>´</mo> </mover> <mtext>t</mtext> </mrow> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi>C</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">⟶</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> for <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_817_Article_IEq3.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(\pi _1^{\acute{\textrm{e}}\textrm{t}}(C)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi>π</mi> <mn>1</mn> <mrow> <mover accent="true"> <mtext>e</mtext> <mo>´</mo> </mover> <mtext>t</mtext> </mrow> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi>C</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> where <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_817_Article_IEq4.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\beta \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>β</mi> </math></EquationSource> </InlineEquation> is a surjective homomorphism of finite groups with prime-to-<i>p</i> kernel <i>H</i>, we discuss when an <i>H</i>-cover of the <i>G</i>-cover of <i>C</i> corresponding to <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_817_Article_IEq5.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="TEX">\(\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>α</mi> </math></EquationSource> </InlineEquation> is a solution. When <i>H</i> is abelian and <i>G</i> is a <i>p</i>-group, some necessary and sufficient conditions for the solvability of the embedding problems are given in terms of the action of <i>G</i> on a certain generalization of <i>m</i>-torsion of the Picard group.</p>

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A criterion for solving embedding problems for the étale fundamental group of curves

  • Manish Kumar,
  • Poulami Mandal

摘要

Let C be an affine curve over an algebraically closed field k of characteristic \(p>0\) p > 0 . Given an embedding problem \((\beta :\Gamma \longrightarrow G, \alpha : \pi ^{\acute{\textrm{e}}\textrm{t}}_1(C)\longrightarrow G)\) ( β : Γ G , α : π 1 e ´ t ( C ) G ) for \(\pi _1^{\acute{\textrm{e}}\textrm{t}}(C)\) π 1 e ´ t ( C ) where \(\beta \) β is a surjective homomorphism of finite groups with prime-to-p kernel H, we discuss when an H-cover of the G-cover of C corresponding to \(\alpha \) α is a solution. When H is abelian and G is a p-group, some necessary and sufficient conditions for the solvability of the embedding problems are given in terms of the action of G on a certain generalization of m-torsion of the Picard group.