Bourbaki

Corollary 2

Tag 0ABS, permanent. Cite it as [Bourbaki, Tag 0ABS].

Lie Groups and Lie Algebras, chapter III, § 3. Passage from a Lie group to its Lie algebra

Suppose that G is finite-dimensional. Let (e1,…,en)(e_1, \ldots, e_n) be a basis of L(G)L(G), (e1∗,…,en∗)(e_1^*, \ldots, e_n^*) the dual basis, (cijk)(c_{ijk}) the constants of structure of L(G)L(G) relative to the basis (e1,…,en)(e_1, \ldots, e_n) and ωi\omega_i (resp. ωi′\omega'_i) the left (resp. right) invariant differential form on G with values in K such that (ωi)e=ei∗(\omega_i)_e = e_i^* (resp. (ωi′)e=ei∗(\omega'_i)_e = e_i^*). Then

dωk+∑i<jcijkωi∧ωj=0(k=1,2,…,n) d\omega_k + \sum_{i < j} c_{ijk} \omega_i \wedge \omega_j = 0 \quad (k = 1, 2, \ldots, n)
dωk′−∑i<jcijkωi′∧ωj′=0(k=1,2,…,n). d\omega'_k - \sum_{i < j} c_{ijk} \omega'_i \wedge \omega'_j = 0 \quad (k = 1, 2, \ldots, n).
If r<sr < s,
(dωk)e(er,es)=−(ωk)e([er,es])=−∑icrsi(ωk)e(ei)=−crsk=−∑i<jcijk(ωi∧ωj)e(er,es). (d\omega_k)_e(e_r, e_s) = -(\omega_k)_e([e_r, e_s]) = -\sum_i c_{rsi} (\omega_k)_e(e_i) = -c_{rsk} = -\sum_{i < j} c_{ijk} (\omega_i \wedge \omega_j)_e(e_r, e_s).
The argument is similar for the ωk′\omega'_k.

Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.

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Cites

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Transcribed from the printed volume. Not translated.