Abstract
A semisimple element
s
of a connected reductive group
G
is called quasi-isolated (respectively isolated) if
C
G
(
s
) (respectively (
s
)) is not contained in a Levi subgroup of a proper parabolic subgroup of
G
. We study properties of quasi-isolated semisimple elements and give a classification in terms of the affine Dynkin diagram of
G
. Tables are provided for adjoint simple groups.
1991 Mathematics Subject Classification:
ACKNOWLEDGMENTS
We wish to thank F. Digne, J. Michel and M. Enguehard for their valuable comments on this work.
Notes
#Communicated by J. Alev.