Bourbaki

Corollary

Tag 01D7, permanent. Cite it as [Bourbaki, Tag 01D7].

Lie Groups and Lie Algebras, chapter IX, § 4. Root system associated to a compact group

Let ee be a framing of (G,T)(G,T) and let E be the group of automorphisms of G that leave ee stable. Then Aut(G) is the semi-direct product of E by Int(G), and Aut(G,T,T) is the semi-direct product of E by Int(G) ∩\cap Aut(G,T,T) == IntG(NG(T))_G(N_G(T)).

Indeed, every element of Aut(G) transforms ee into a framing of G. By Prop. 19, every coset of Aut(G) modulo Int(G) meets E in a single point, hence the first assertion. The second is proved in the same way.

Bourbaki sets the proof directly after the statement, and the corpus does not separate them, so what is above is the statement and its proof together.

Cited by

Nothing.

Cites

Transcribed from the printed volume. Not translated.