What is the transformation rule for vector-covector derivatives?

In summary, the conversation discusses the transformation of the expression X^b (d(Aa)/d(x^b) - d(Ab)/d(x^a)) under a smooth change of coordinates. It is noted that the derivatives are partial and using the transformation rules for the vector and covector results in four terms, two of which give the desired transformation rule. The remaining two terms are shown to disappear due to containing a term involving the mixed partial derivative. The person asking for hints realizes their mistake in differentiating with respect to the wrong coordinate system and is able to successfully use the chain rule and differentiate with respect to the correct coordinate system to obtain the desired transformation.
  • #1
deadringer
33
0

Homework Statement


We have a vector X^a (n.b ^ indicates superscript) and covector Aa. We need to show that
X^b (d(Aa)/d(x^b) - d(Ab)/d(x^a))

transforms correctly under an artbitrary smooth change of coords. N.b the derivatives are partial.

By using the transformation rules for the vector and covector respectively I get four terms, two of which give us the required transformation rule. I can't get the other two to disappear. I'd appreciate any hints.
 
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  • #2
When I do it I find the other two terms vanish because they contain a term like [tex] \frac{ \partial^2 f}{\partial x \partial y}-\frac{\partial^2 f}{\partial y \partial x}[/tex].
 
Last edited:
  • #3
I managed to get this. I was differentiating with respect to the wrong coordinate system, which messed up the calculation. I then tried using the chain rule and differentiating with respect to the other coord system and it all fell out.
 

1. What is a GR-tensor transformation?

A GR-tensor transformation refers to the mathematical process of transforming a tensor under a change of coordinates in the theory of General Relativity (GR). It involves using the tensor transformation law to convert the components of a tensor from one coordinate system to another.

2. Why is tensor transformation important in GR?

In GR, the laws of physics are described using tensors, which are mathematical objects that represent physical quantities. Since tensors are dependent on the coordinate system used, it is necessary to perform tensor transformations in order to ensure the laws of physics remain consistent regardless of the choice of coordinates.

3. How is a tensor transformed in GR?

In GR, tensors are transformed using the tensor transformation law, which involves multiplying the components of the original tensor by a set of transformation coefficients. These coefficients are derived from the Jacobian matrix, which describes the relationship between the old and new coordinates.

4. Can GR-tensor transformation be applied to all tensors?

Yes, GR-tensor transformation can be applied to all tensors, including scalars, vectors, and higher-order tensors. The transformation law remains the same, but the number of components and transformation coefficients may vary depending on the type and order of the tensor.

5. Is there a specific notation for GR-tensor transformation?

Yes, there are various notations used to represent GR-tensor transformations, such as index notation, Einstein notation, and abstract index notation. These notations allow for a more compact and concise representation of tensors and their transformations.

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