Bourbaki

Proposition 46

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

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

Let h∈G,x∈Th(G)h \in G, x \in T_h(G) and a∈L(G)a \in L(G). Let ϕ\phi be the mapping (g,g′)↦gg′g−1(g, g') \mapsto gg'g^{-1} of G×GG \times G into GG. The image y of (a,x)∈Te(G)×Th(G)(a, x) \in T_e(G) \times T_h(G) under T(e,h)(ϕ)T_{(e, h)}(\phi) is y=x+h((Ad h−1)a−a)y = x + h((\mathrm{Ad}\,h^{-1})a - a). We have

y=(T(e,h)ϕ)(a⊗εh+εe⊗x)=a⊤εh+εe⊤x=a∗εh−εh∗a+x=h((Ad h−1)a)−ha+x. \begin{align*} y &= (T_{(e, h)}\phi)(a \otimes \varepsilon_h + \varepsilon_e \otimes x) \\ &= a \top \varepsilon_h + \varepsilon_e \top x \\ &= a * \varepsilon_h - \varepsilon_h * a + x \\ &= h((\mathrm{Ad}\,h^{-1})a) - ha + x. \end{align*}

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

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Transcribed from the printed volume. Not translated.