Differentiating Composition of Smooth Functions

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SUMMARY

The discussion focuses on the composition of smooth functions, specifically demonstrating that the pushforward of the composition of two smooth functions, \( h = g \circ f \), is equal to the composition of their respective pushforwards, \( h_{*} = g_{*} \circ f_{*} \). The proof utilizes the properties of manifolds and derivations, confirming that for any derivation \( D \) at point \( p \in M \), the relationship holds true through the application of the chain rule in differential geometry. The functions \( f \) and \( g \) are defined as \( C^\infty \) functions, ensuring smoothness in the composition.

PREREQUISITES
  • Understanding of smooth manifolds and their properties
  • Familiarity with \( C^\infty \) functions and their definitions
  • Knowledge of derivations in the context of differential geometry
  • Basic concepts of pushforward in manifold theory
NEXT STEPS
  • Study the properties of \( C^\infty \) functions in manifold theory
  • Learn about derivations and their applications in differential geometry
  • Explore the concept of pushforward and its implications in smooth mappings
  • Investigate examples of smooth function compositions in various manifolds
USEFUL FOR

Mathematicians, students of differential geometry, and anyone studying the properties of smooth functions and their compositions in manifold theory.

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Homework Statement



Let f: M \rightarrow N, g:N \rightarrow K, and h = g \circ f : M \rightarrow K. Show that h_{*} = g_{*} \circ f_{*}.

Proof:

Let M,N and K be manifolds and f and g be C^\infinity functions.

Let p \in M. For any u \in F^{\infinity}(g(f((p))) and any derivation D at p.

[g \circ f)_* D](u) = D(u \circ g \circ f) = (f_{*}D)(u \circ g) = (g_{*}(f_{*}D))(u)

Homework Equations


The Attempt at a Solution

 
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Should be C^\infty and F^\infty(g(f((p)))
 

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