{"title":"The Lyndon–Demushkin method and crystalline lifts of G2-valued Galois representations","authors":"Zhongyipan Lin","doi":"10.2140/ant.2025.19.415","DOIUrl":null,"url":null,"abstract":"<p>We develop obstruction theory for lifting characteristic-<math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>p</mi></math> local Galois representations valued in reductive groups of type <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi>B</mi></mrow><mrow><mi>l</mi></mrow></msub></math>, <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi>C</mi></mrow><mrow><mi>l</mi></mrow></msub></math>, <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi>D</mi></mrow><mrow><mi>l</mi></mrow></msub></math> or <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi>G</mi></mrow><mrow><mn>2</mn></mrow></msub></math>. An application of the Emerton–Gee stack then reduces the existence of crystalline lifts to a purely combinatorial problem when <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>p</mi></math> is not too small. </p><p> As a toy example, we show for all local fields <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>K</mi><mo>∕</mo><msub><mrow><mi>ℚ</mi></mrow><mrow><mi>p</mi></mrow></msub></math>, with <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>p</mi>\n<mo>></mo> <mn>3</mn></math>, all representations <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mover accent=\"true\"><mrow><mi>ρ</mi></mrow><mo accent=\"true\">¯</mo></mover>\n<mo>:</mo> <msub><mrow><mi>G</mi></mrow><mrow><mi>K</mi></mrow></msub>\n<mo>→</mo> <msub><mrow><mi>G</mi></mrow><mrow><mn>2</mn></mrow></msub><mo stretchy=\"false\">(</mo><msub><mrow><mover accent=\"true\"><mrow><mi mathvariant=\"double-struck\">𝔽</mi></mrow><mo accent=\"true\">¯</mo></mover></mrow><mrow><mi>p</mi></mrow></msub><mo stretchy=\"false\">)</mo></math> admit a crystalline lift <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>ρ</mi>\n<mo>:</mo> <msub><mrow><mi>G</mi></mrow><mrow><mi>K</mi></mrow></msub>\n<mo>→</mo> <msub><mrow><mi>G</mi></mrow><mrow><mn>2</mn></mrow></msub><mo stretchy=\"false\">(</mo><msub><mrow><mover accent=\"true\"><mrow><mi>ℤ</mi></mrow><mo accent=\"true\">¯</mo></mover></mrow><mrow><mi>p</mi></mrow></msub><mo stretchy=\"false\">)</mo></math>, where <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi>G</mi></mrow><mrow><mn>2</mn></mrow></msub></math> is the exceptional Chevalley group of type <math display=\"inline\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mrow><mi>G</mi></mrow><mrow><mn>2</mn></mrow></msub></math>. </p>","PeriodicalId":50828,"journal":{"name":"Algebra & Number Theory","volume":"376 1","pages":""},"PeriodicalIF":0.9000,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Algebra & Number Theory","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.2140/ant.2025.19.415","RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
We develop obstruction theory for lifting characteristic- local Galois representations valued in reductive groups of type , , or . An application of the Emerton–Gee stack then reduces the existence of crystalline lifts to a purely combinatorial problem when is not too small.
As a toy example, we show for all local fields , with , all representations admit a crystalline lift , where is the exceptional Chevalley group of type .
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