Pushforward/Pullback of Vector Field

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Discussion Overview

The discussion revolves around the concepts of pushforward and pullback of vector fields, specifically examining different formulations and interpretations of these operations in the context of differential geometry. Participants explore the relationship between various equations and their implications for evaluating vector fields.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant presents a formula for the pushforward and seeks clarification on its reconciliation with a more familiar equation.
  • Another participant suggests that the notation used may complicate the understanding of the point of evaluation, providing a reference to additional material for clarity.
  • A participant introduces a specific example involving a curve and a left action, questioning the correctness of their derivation related to the left action and its derivative.
  • A subsequent reply confirms the correctness of the derivation presented in the previous post.

Areas of Agreement / Disagreement

Participants express varying interpretations of the pushforward and pullback operations, and while there is some agreement on the correctness of specific derivations, the overall discussion remains exploratory without a consensus on the initial equations presented.

Contextual Notes

The discussion includes various formulations and interpretations of the pushforward and pullback, which may depend on specific definitions and contexts. The relationship between the equations discussed is not fully resolved, and assumptions regarding the notation and evaluation points are not explicitly stated.

knowwhatyoudontknow
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Pushforward of vector field.
I am looking at the following document. In section 2.3 they have the formula for the pushforward:

f*(X) := Tf o X o f-1

I am having trouble trying to reconcile this with the more familiar equation:

f*(X)(g ) = X(g o f)

Any help would be appreciated.
 
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I read this as an unfortunate way to reference the point of evaluation: Given ##f\, : \,M\longrightarrow N## we need a point ##p\in M## to evaluate at: ##p=f^{-1}(q)## for ##q\in N.##

Have a look at eq. 38 at the end in https://www.physicsforums.com/insights/pantheon-derivatives-part-iii/
I also collected a few of the many ways to write it.
 
OK. Thanks. If I have γ(t) = exp(tv) so that γ(0) = p and γ'(0) = v and Lg is a left action then is the following correct?

Lg*γ'(0) = (Lg o γ(t))'(0)

= d/dt|t=0Lg(γ(t))

= dLg/dt|t=0.v

= gv

In other words dLg/dt|t=0 ≡ g
 
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knowwhatyoudontknow said:
OK. Thanks. If I have γ(t) = exp(tv) so that γ(0) = p and γ'(0) = v and Lg is a left action then is the following correct?

Lg*γ'(0) = (Lg o γ(t))'(0)

= d/dt|t=0Lg(γ(t))

= dLg/dt|t=0.v

= gv

In other words dLg/dt|t=0 ≡ g
Looks ok to me.
 
Great. Thanks.
 

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