Changing Dot Product to Simple Multiplication

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Discussion Overview

The discussion revolves around the transformation of the dot product into simple multiplication within the context of tensor calculus and the relationship between basis vectors and their derivatives. Participants explore how to express certain mathematical relationships without explicitly using the dot product.

Discussion Character

  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant inquires about how to express the partial derivative \(\partial_{c} e^{a}\) without involving the dot product, specifically in the equation \(e_{b} \cdot \partial_{c} e^{a} = -\Gamma^{a}_{bc}\).
  • Another participant suggests that \(\Gamma^{a}_{bc}\) can be expressed as \(e_{a} \cdot \partial_{c} e_{b}\), indicating a potential relationship between the components of the basis vectors and their derivatives.
  • A different participant notes that knowing the dot product of two vectors equating to a scalar does not provide enough information to isolate one of the vectors without additional context or data.
  • Further elaboration is provided on the expression of the partial derivative of the basis vector \(e_{b}\) in terms of the Christoffel symbols \(\Gamma^{j}_{bc}\) and the coordinate basis vectors, suggesting a method to relate these components to the metric tensor.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of isolating the partial derivative without additional information, indicating that the discussion remains unresolved with multiple competing perspectives on the approach to the problem.

Contextual Notes

There are limitations regarding the specific symbols and their meanings, as well as the assumptions underlying the relationships between the vectors and their derivatives. The discussion does not resolve these ambiguities.

Halaaku
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How does one change the dot product such that there is no dot product in between, just plain multiplication? For example, in the following:
eb.[itex]\partial[/itex]cea=-[itex]\Gamma[/itex]a bc

How do I get just an expression for [itex]\partial[/itex]cea?
 
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Here [itex]\Gamma[/itex]a bc = ea.∂ceb
 
I have no knowledge of the particular symbols. However if you have the dot product of two vectors equal to a scalar, you cannot get one of the vectors from the scalar without further information. It is not enough just to know the other vector.
 
Halaaku said:
Here [itex]\Gamma[/itex]a bc = ea.∂ceb

The partial derivative of the coordinate basis vector eb with respect to the spatial coordinate xc is a vector, which can be expressed at a given point as a linear combination of the coordinate basis vectors:

[tex]\frac{\partial e_b}{\partial x^c}=\Gamma^j_{bc}e_j[/tex]

The [itex]\Gamma 's[/itex] are the components of the vector. If we dot this equation with the duel basis vector ea, we get:
[tex]e^a\centerdot\frac{\partial e_b}{\partial x^c}=\Gamma^a_{bc}[/tex]

The trick is to figure out how to represent the [itex]\Gamma 's[/itex] in terms of the partial spatial derivatives of the components of the metric tensor.
 

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