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PropositionStatement: AI-adaptedProof: AI-adaptedPipeline-generatedprecheck passjudge pass (gpt-5.6-terra)audited 2026-09-14
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  • Literature-sourced: the exact statement appears in a cited source; only wording and notation differ.
  • AI-adapted: a semantically identical restatement of literature-sourced material, modulo indexing, notation, and boundary cases adopted by the library.
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Exponential map is natural for Lie-group homomorphisms

Statement

Assume ACω. If F:G→H is a homomorphism of finite-dimensional real Lie groups, then for every X∈g=TeG,

F(exp⁡GX)=exp⁡H(dFeX).

The countable-choice assumption is used exactly through the supplied one-parameter-subgroup/exponential characterization.

Facts & Assumptions

Given: ACω, a Lie-group homomorphism F:G→H, and X∈g=TeG.

[F1]

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

[F2]

A one-parameter subgroup with initial velocity Y is uniquely the curve t↦exp⁡(tY). One-parameter subgroups are exactly exponentials.

[F3]

The map F is smooth, preserves identities, and satisfies F(gh)=F(g)F(h). Lie-group homomorphism, isomorphism, and automorphism.

[F4]

Differentials of smooth maps obey the chain rule. The chain rule for differentials of smooth maps.

Proof

technique · direct
1.1F2F3

By [F2], aX(t)=exp⁡G(tX) is a one-parameter subgroup. Since [F3] makes F a smooth group homomorphism, the composite c(t)=F(aX(t)) is a one-parameter subgroup of H.

2.1F2F3F4step 1.1

The same characterization [F2] gives aX′(0)=X. Hence the chain rule [F4] yields c′(0)=dFe(aX′(0))=dFeX.

3.1F2step 1.1step 2.1

Apply [F2] in H: the unique one-parameter subgroup with initial velocity dFeX is t↦exp⁡H(t dFeX). Steps 1.1--2.1 identify c with this curve. Evaluating at t=1 gives F(exp⁡GX)=exp⁡H(dFeX).

4.1F1F2F3F4step 1.1step 2.1step 3.1∎

Both Lie groups are nonempty and boundaryless. Zero-dimensional source or target Lie algebras and dimension one require no change, including X=0. The one-parameter curves are global, so no endpoint issue occurs. No metric or nondegeneracy condition occurs. The only choice use is the stated ACω, inherited through [F2]; composition with one supplied homomorphism and evaluation at one add no choice. No biconditional is asserted.

Depends on

Dependency tree · 2 levels

Sources