{"title":"Supersingular curves of genus four in characteristic two","authors":"Dušan Dragutinović","doi":"10.1090/proc/16792","DOIUrl":null,"url":null,"abstract":"<p>We describe the intersection of the Torelli locus <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"j left-parenthesis script upper M 4 Superscript c t Baseline right-parenthesis equals script upper J 4\">\n <mml:semantics>\n <mml:mrow>\n <mml:mi>j</mml:mi>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:msubsup>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi class=\"MJX-tex-caligraphic\" mathvariant=\"script\">M</mml:mi>\n </mml:mrow>\n <mml:mn>4</mml:mn>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi>c</mml:mi>\n <mml:mi>t</mml:mi>\n </mml:mrow>\n </mml:msubsup>\n <mml:mo stretchy=\"false\">)</mml:mo>\n <mml:mo>=</mml:mo>\n <mml:msub>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi class=\"MJX-tex-caligraphic\" mathvariant=\"script\">J</mml:mi>\n </mml:mrow>\n <mml:mn>4</mml:mn>\n </mml:msub>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">j(\\mathcal {M}_4^{ct}) = \\mathcal {J}_4</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> with Newton and Ekedahl-Oort strata related to the supersingular locus in characteristic 2. We show that the locus of supersingular Jacobians <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"script upper S 4 intersection script upper J 4\">\n <mml:semantics>\n <mml:mrow>\n <mml:msub>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi class=\"MJX-tex-caligraphic\" mathvariant=\"script\">S</mml:mi>\n </mml:mrow>\n <mml:mn>4</mml:mn>\n </mml:msub>\n <mml:mo>∩<!-- ∩ --></mml:mo>\n <mml:msub>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi class=\"MJX-tex-caligraphic\" mathvariant=\"script\">J</mml:mi>\n </mml:mrow>\n <mml:mn>4</mml:mn>\n </mml:msub>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">\\mathcal {S}_4\\cap \\mathcal {J}_4</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> in characteristic 2 is pure of dimension three. One way to obtain that result uses an analysis of the data of smooth genus four curves and principally polarized abelian fourfolds defined over <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"double-struck upper F 2\">\n <mml:semantics>\n <mml:msub>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi mathvariant=\"double-struck\">F</mml:mi>\n </mml:mrow>\n <mml:mn>2</mml:mn>\n </mml:msub>\n <mml:annotation encoding=\"application/x-tex\">\\mathbb {F}_2</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula>, and another involves a more careful study of some relevant Ekedahl-Oort loci.</p>","PeriodicalId":20696,"journal":{"name":"Proceedings of the American Mathematical Society","volume":null,"pages":null},"PeriodicalIF":0.8000,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Proceedings of the American Mathematical Society","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1090/proc/16792","RegionNum":3,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 1
Abstract
We describe the intersection of the Torelli locus j(M4ct)=J4j(\mathcal {M}_4^{ct}) = \mathcal {J}_4 with Newton and Ekedahl-Oort strata related to the supersingular locus in characteristic 2. We show that the locus of supersingular Jacobians S4∩J4\mathcal {S}_4\cap \mathcal {J}_4 in characteristic 2 is pure of dimension three. One way to obtain that result uses an analysis of the data of smooth genus four curves and principally polarized abelian fourfolds defined over F2\mathbb {F}_2, and another involves a more careful study of some relevant Ekedahl-Oort loci.
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