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Publication

Double centralizers of unipotent elements in simple algebraic groups of type $E_7$ and $E_8$

Iulian Ion Simion
2015
Journal paper

Abstract

This article addresses questions about the double centralizer of unipotent elements u in simple algebraic groups G of type and defined over algebraically closed fields of bad characteristic. We use the method developed in [14] to determine , deduce its dimension and recognize if it is an overgroup for u. The method used requires explicit representatives of the component group of which we produce in all cases. This article extends the results of [14] to all exceptional type groups.

Official source

https://infoscience.epfl.ch/record/268020?ln=en

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Related concepts

Related publications

Double centralizers of unipotent elements in simple algebraic groups of type G(2), F-4 and E-6

Iulian Ion Simion

Let u be a unipotent element of a simple algebraic group G over a field k of characteristic p. We develop a method for computing the connected component of Z(C-G(u)) in the cases where p is positive and both it and the rank of G are small enough. The method is then carried out for G of type G(2), F-4 and E-6 in bad characteristic. (C) 2013 Elsevier Inc. All rights reserved.

Academic Press Inc Elsevier Science2013

Let

u

be a unipotent element of a simple algebraic group

G

over a field

k

of characteristic

p

. We develop a method for computing the connected component of

Z(C_G(u))

in the cases where

p

is positive and both it and the rank of

G

are small enough. The method is then carried out for

G

of type

G_2

F_4

and

E_6

in bad characteristic.

2013

Irreducibility of disconnected subgroups of exceptional algebraic groups

Soumaïa Nadia Ghandour

This dissertation is concerned with the study of irreducible embeddings of simple algebraic groups of exceptional type. It is motivated by the role of such embeddings in the study of positive dimensional closed subgroups of classical algebraic groups. The classification of the maximal closed connected subgroups of simple algebraic groups was carried out by E. B. Dynkin, G. M. Seitz and D. M. Testerman. Their analysis for the classical groups was based primarily on a striking result: if G is a simple algebraic group and ø : G → SL(V ) is a tensor indecomposable irreducible rational representation then, with specified exceptions, the image of G is maximal among closed connected subgroups of one of the classical groups SL(V), Sp(V ) or SO(V ). In the case of closed, not necessarily connected, subgroups of the classical groups, one is interested in considering irreducible embeddings of simple algebraic groups and their automorphism groups: given a simple algebraic group Y defined over an algebraically closed field K, one is led to study the embeddings G < Aut(Y ), where G and Aut(Y ) are closed subgroups of SL(V ) and V is an irreducible rational KY -module on which G acts irreducibly. A partial analysis of such embeddings in the case of classical algebraic groups Y was carried out by B. Ford. We purpose to classify all triples (G, Y, V ) where Y is a simple algebraic group of exceptional type, defined over an algebraically closed field K of characteristic p > 0, G is a closed non-connected positive dimensional subgroup of Y and V is a nontrivial irreducible rational KY -module such that V|G is irreducible. We obtain a precise description of such triples (G, Y, V ).

EPFL2008

Let

u