Are Lie Brackets and Their Derivatives Equivalent in Vector Field Calculations?

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Homework Help Overview

The discussion revolves around the properties and calculations involving Lie brackets in the context of vector fields. The original poster presents two questions related to proving an identity involving Lie derivatives and calculating a specific Lie bracket.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to prove an identity involving Lie derivatives and expresses uncertainty about the equivalence of two expressions. They also question the expansion of a Lie bracket calculation involving specific vector fields and derivatives.

Discussion Status

Some participants provide feedback on the original poster's calculations, noting a missing vector field in one of the expressions. The discussion reflects a collaborative effort to clarify the original poster's understanding of the concepts involved.

Contextual Notes

The original poster indicates confusion regarding the use of certain derivatives and the expansion of Lie brackets, suggesting a need for further exploration of these concepts.

pleasehelpmeno
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Hi i have two questions:
1) When asked to prove [itex]\mathcal{L}_{u}\mathcal{L}_{v}W - \mathcal{L}_{v}\mathcal{L}_{u}W = \mathcal{L}_{[u,v]}[/itex].

I achieved [itex][u,v]w = \mathcal{L}_{[u,v]}[/itex]. This was found by appliying a scalar field <b> to the LHS and simplifying and expanding using + and scalar linearitys to get [itex][u,v]w[/itex] but I am not sure if these are equivalent.

2) When asked to calculate the Lie bracket [X,Y] where [itex]X=5x^{2}\frac{\partial}{\partial t}-4t\frac{\partial}{\partial x}[/itex] and [itex]Y= y\frac{\partial}{\partial t} + t\frac{\partial}{\partial y}[/itex] is this equivalent to:
[itex]\left((5x^{2}\frac{\partial}{\partial t} -4t\frac{\partial}{\partial x})\frac{\partial (y\frac{\partial}{\partial t} + t\frac{\partial}{\partial y})}{\partial x^{a}}-(y\frac{\partial}{\partial t} + t\frac{\partial}{\partial y})\frac{\partial (5x^{2}\frac{\partial}{\partial t}-4t\frac{\partial}{\partial x})}{\partial x}\right)\frac{\partial}{\partial x^{b}}[/itex]

and if so can it be expanded any further I am not so sure but i don't fully understand [itex]\frac{\partial}{\partial x^{a}}[/itex] derivatives.
 
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never mind figured it out
 
I'm sure you're missing out the vector field W in the RHS of 1).
 
yeah i figured them out and yeah missed it off, thx
 

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