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CorollaryStatement: AI-adaptedProof: AI-adaptedPipeline-generatedprecheck passjudge pass (gpt-5.6-terra)audited 2026-09-14
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  • AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
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The exponential map is a local diffeomorphism at zero

Statement

Assume ACω. Let G be a finite-dimensional real Lie group with identity e and Lie algebra g. There are open neighborhoods V⊆g of 0 and U⊆G of e such that

exp⁡G∣V:V⟶U

is a diffeomorphism. The countable-choice assumption is inherited exactly from the supplied smoothness and identity-differential theorem.

Facts & Assumptions

Given: ACω and a finite-dimensional real Lie group G with identity e and Lie algebra g.

[F1]

ACω is countable choice. The Axiom of Countable Choice (ACω).

[F2]

Assuming ACω, exp⁡G is smooth, exp⁡G(0)=e, and d(exp⁡G)0=id⁡g. The Lie-group exponential map is smooth with identity differential at zero.

[F3]

A smooth map whose differential at a point is an isomorphism restricts to a diffeomorphism between neighborhoods of that point and its image. The smooth inverse function theorem on manifolds.

Proof

technique · direct
1.1F2

By [F2], exp⁡G is smooth, sends 0 to e, and its differential at 0 is the identity of g, hence a linear isomorphism.

2.1F2F3step 1.1

Apply [F3] to F=exp⁡G at 0. Using step 1.1, obtain open neighborhoods V of 0 and U of e=exp⁡G(0) such that exp⁡G∣V:V→U is a diffeomorphism.

3.1F1F2F3step 1.1step 2.1∎

Lie groups are nonempty and boundaryless. If dim⁡G=0, then V={0} and U={e} may be chosen open and the restriction is the unique diffeomorphism; in dimension one the same inverse function theorem applies. The neighborhoods are open and contain their named points, so there is no endpoint issue. No metric or nondegeneracy condition occurs. The only choice use is the stated ACω, inherited through [F2]; applying [F3] once adds no family choice. No biconditional is asserted.

Depends on

Dependency tree · 2 levels

Sources