
Journal of Lie Theory 22 (2012), No. 4, 9491024 Copyright Heldermann Verlag 2012 Maximal Subgroups of Compact Lie Groups Fernando Antoneli Escola Paulista de Medicina, Universidade Federal de São Paulo, 04039062 São Paulo  SP, Brazil fernando.antoneli@unifesp.br Michael Forger Inst. de Matemática e Estatística, Universidade de São Paulo, PO Box 66281, 05315970 São Paulo  SP, Brazil forger@ime.usp.br Paola Gaviria Inst. de Matemática e Estatística, Universidade de São Paulo, PO Box 66281, 05315970 São Paulo  SP, Brazil pgaviria@ime.usp.br This report aims at giving a general overview on the classification of the maximal subgroups of compact Lie groups (not necessarily connected). In the first part, it is shown that these fall naturally into three types: (1) those of trivial type, which are simply defined as inverse images of maximal subgroups of the corresponding component group under the canonical projection and whose classification constitutes a problem in finite group theory, (2) those of normal type, whose connected onecomponent is a normal subgroup, and (3) those of normalizer type, which are the normalizers of their own connected onecomponent. It is also shown how to reduce the classification of maximal subgroups of the last two types to: (2) the classification of the finite maximal Σinvariant subgroups of centerfree connected compact simple Lie groups and (3) the classification of the Σprimitive subalgebras of compact simple Lie algebras, where Σ is a subgroup of the corresponding outer automorphism group. In the second part, we explicitly compute the normalizers of the primitive subalgebras of the compact classical Lie algebras (in the corresponding classical groups), thus arriving at the complete classification of all (nondiscrete) maximal subgroups of the compact classical Lie groups. Keywords: Lie groups, Lie algebras, Compact groups, Maximal subgroups. MSC: 22E15 [ Fulltextpdf (721 KB)] for subscribers only. 