{"title":"The -invariant over splitting fields of Tits algebras","authors":"Maksim Zhykhovich","doi":"10.1112/s0010437x24007255","DOIUrl":null,"url":null,"abstract":"<p>We describe the <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240910155753172-0985:S0010437X24007255:S0010437X24007255_inline2.png\"><span data-mathjax-type=\"texmath\"><span>$J$</span></span></img></span></span>-invariant of a semisimple algebraic group <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240910155753172-0985:S0010437X24007255:S0010437X24007255_inline3.png\"><span data-mathjax-type=\"texmath\"><span>$G$</span></span></img></span></span> over a generic splitting field of a Tits algebra of <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240910155753172-0985:S0010437X24007255:S0010437X24007255_inline4.png\"><span data-mathjax-type=\"texmath\"><span>$G$</span></span></img></span></span> in terms of the <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240910155753172-0985:S0010437X24007255:S0010437X24007255_inline5.png\"><span data-mathjax-type=\"texmath\"><span>$J$</span></span></img></span></span>-invariant over the base field. As a consequence we prove a 10-year-old conjecture of Quéguiner-Mathieu, Semenov, and Zainoulline on the <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240910155753172-0985:S0010437X24007255:S0010437X24007255_inline6.png\"><span data-mathjax-type=\"texmath\"><span>$J$</span></span></img></span></span>-invariant of groups of type <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240910155753172-0985:S0010437X24007255:S0010437X24007255_inline7.png\"><span data-mathjax-type=\"texmath\"><span>$\\mathrm {D}_n$</span></span></img></span></span>. In the case of type <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240910155753172-0985:S0010437X24007255:S0010437X24007255_inline8.png\"><span data-mathjax-type=\"texmath\"><span>$\\mathrm {D}_n$</span></span></img></span></span> we also provide explicit formulas for the first component and in some cases for the second component of the <span><span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240910155753172-0985:S0010437X24007255:S0010437X24007255_inline9.png\"><span data-mathjax-type=\"texmath\"><span>$J$</span></span></img></span></span>-invariant.</p>","PeriodicalId":55232,"journal":{"name":"Compositio Mathematica","volume":null,"pages":null},"PeriodicalIF":1.3000,"publicationDate":"2024-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Compositio Mathematica","FirstCategoryId":"100","ListUrlMain":"https://doi.org/10.1112/s0010437x24007255","RegionNum":1,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATHEMATICS","Score":null,"Total":0}
引用次数: 0
Abstract
We describe the $J$-invariant of a semisimple algebraic group $G$ over a generic splitting field of a Tits algebra of $G$ in terms of the $J$-invariant over the base field. As a consequence we prove a 10-year-old conjecture of Quéguiner-Mathieu, Semenov, and Zainoulline on the $J$-invariant of groups of type $\mathrm {D}_n$. In the case of type $\mathrm {D}_n$ we also provide explicit formulas for the first component and in some cases for the second component of the $J$-invariant.
期刊介绍:
Compositio Mathematica is a prestigious, well-established journal publishing first-class research papers that traditionally focus on the mainstream of pure mathematics. Compositio Mathematica has a broad scope which includes the fields of algebra, number theory, topology, algebraic and differential geometry and global analysis. Papers on other topics are welcome if they are of broad interest. All contributions are required to meet high standards of quality and originality. The Journal has an international editorial board reflected in the journal content.