Bourbaki

Proposition 3

Tag 0A6W, permanent. Cite it as [Bourbaki, Tag 0A6W].

Lie Groups and Lie Algebras, chapter II, § 8. Convergence of the Hausdorff series (ultrametric case)

Let GG be the ball {x∈g∣∥x∥<aθ}\{ x \in g | \| x \| < a^{\theta} \}. The analytic mapping

h:G×G→G h : G \times G \to G
makes GG into a group in which 00 is the identity element and −x-x is the inverse of xx for all x∈Gx \in G. Moreover, if RR is a real number such that 0<R<aθ0 < R < a^{\theta}, the ball
{x∈g∣∥x∥<R} \{ x \in g | \| x \| < R \}
(resp. {x∈g∣∥x∥≤R}\{ x \in g | \| x \| \leq R \}) is an open subgroup of GG.

As H(U,−U)=0H(U, -U) = 0 and H(0,U)=H(U,0)=UH(0, U) = H(U, 0) = U, h(x,−x)=0h(x, -x) = 0 and

h(0,x)=h(x,0)=x h(0, x) = h(x, 0) = x
for all x∈Gx \in G. It therefore remains to prove the associativity formula
h(h(x,y),z)=h(x,h(y,z))for x,y,z in G. h(h(x, y), z) = h(x, h(y, z)) \quad \text{for } x, y, z \text{ in } G.
As
H(H(U,V),W)=H(U,H(V,W)) H(H(U, V), W) = H(U, H(V, W))
in L^({U,V,W})\hat{L}(\{ U, V, W \}) (§ 6, no. 5, Proposition 4), we have
H~∘(H~×Idg)=H~∘(Idg×H~) \tilde{H} \circ (\tilde{H} \times \mathrm{Id}_g) = \tilde{H} \circ (\mathrm{Id}_g \times \tilde{H})
in P^(g×g×g;g)\hat{P}(g \times g \times g; g) (no. 2) and (19) implies (18) by (16) and Differentiable and Analytic Manifolds, R, 4.1.5.

In other words (Chapter III, § 1), GG with the Hausdorff function is a Lie group.

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

Cited by

Cites

Transcribed from the printed volume. Not translated.