Complete reducibility in good characteristic

Let G be a simple algebraic group of exceptional type, over an algebraically closed field of characteristic p \ge 0. A closed subgroup H of G is called G-completely reducible ( G-cr) if whenever H is contained in a parabolic subgroup P of G, it is contained in a Levi subgroup of P. In this paper we...

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Veröffentlicht in:Transactions of the American Mathematical Society 2018-08, Vol.370 (8), p.5279-5340
Hauptverfasser: LITTERICK, ALASTAIR J., THOMAS, ADAM R.
Format: Artikel
Sprache:eng
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Zusammenfassung:Let G be a simple algebraic group of exceptional type, over an algebraically closed field of characteristic p \ge 0. A closed subgroup H of G is called G-completely reducible ( G-cr) if whenever H is contained in a parabolic subgroup P of G, it is contained in a Levi subgroup of P. In this paper we determine the G-conjugacy classes of non- G-cr simple connected subgroups of G when p is good for G. For each such subgroup X, we determine the action of X on the adjoint module L(G) and the connected centraliser of X in G. As a consequence we classify all non- G-cr connected reductive subgroups of G, and determine their connected centralisers. We also classify the subgroups of G which are maximal among connected reductive subgroups, but not maximal among all connected subgroups.
ISSN:0002-9947
1088-6850
DOI:10.1090/tran/7085