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14.1 Why a Lie algebroid?

A tangent bundle gives every direction available at a state. An agent rarely has arbitrary access. Its possible changes are constrained by tools, permissions, schemas, and workflow state. A Lie algebroid separates the space of controlled directions from the changes they realize [ Mackenzie , 2005 ] .

Definition 14.1 Lie algebroid

A Lie algebroid over a manifold \(M\) consists of a vector bundle

\[ \pi :A\longrightarrow M, \]

a Lie bracket \([\cdot ,\cdot ]_A\) on sections \(\Gamma (A)\), and an anchor

\[ \rho :A\longrightarrow TM \]

satisfying

\[ [s,ft]_A = f[s,t]_A + (\rho (s)f)t \]

for sections \(s,t\) and smooth functions \(f\).

The anchor answers “what visible edit occurs?” The bracket answers “how do two controlled edits interact?” The kernel \(\ker \rho \) contains directions with no immediate visible displacement. Such directions can still alter provenance, tool state, routing assumptions, or future compositions.

Geometric object

Agent interpretation

Observable proxy

Failure

Section \(s\)

typed edit or skill policy

named repair operator

not executable in current state

Anchor \(\rho (s)\)

realized artifact or workflow change

diff, tool action, state transition

anchor mismatch

Bracket \([s,t]_A\)

order-sensitive interaction

\(s\! \to t\) versus \(t\! \to s\) contrast

unstable composition

Kernel direction

latent procedural change

trace difference with similar artifact

future hidden regression

Table 14.1 The algebroid separates controlled intent, visible execution, and latent procedural state.