Extracting a matrix from a curl operation

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Discussion Overview

The discussion revolves around the possibility of extracting a 3x3 matrix [A] from a curl operation involving a 3x1 vector B. Participants are exploring the relationship between the curl of the product of a matrix and a vector, specifically questioning the nature and rank of the resulting tensor [C] and its dependence on [A].

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant asks if it is possible to express a tensor [C] in terms of matrix [A] from the equation ∇x([A]B) = [C](∇xB).
  • Another participant suggests that the linearity of the equations allows for testing individual components of [A] to find a solution.
  • A participant reports unsuccessful attempts to find a solution using specific forms of [A], indicating a lack of a general solution.
  • Further discussion reveals that different matrices [A] yield different results for [C], suggesting that a general solution may not exist.
  • One participant concludes that if simple matrices do not yield a valid solution for [C], it implies that variations of [A] may also not be solvable.
  • Another participant confirms that there is no solution for general matrices [A], proposing that only a trivial solution exists (A=a*identity matrix).

Areas of Agreement / Disagreement

Participants generally agree that there is no solution for general matrices [A], with some suggesting that only trivial solutions may exist. However, there is some debate regarding the implications of testing specific matrices and whether this definitively rules out other forms of [A].

Contextual Notes

The discussion is limited by the assumptions made about the nature of the matrices involved and the specific forms tested. There is also uncertainty regarding the generalizability of the results based on the examples provided.

KrayzBlu
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Hello,

I would like to know if it is possible (and the solution, if known, please!) to extract a 3x3 matrix [A] from a curl operation. Specifically, if B is a 3x1 (column) vector,

∇x([A]B) = [C](∇xB)

What is the value of tensor [C]? Would [C] be a 3x3 matrix as well, or a different rank tensor? Can I express [C] in terms of [A]?

Thanks!
 
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The equations are linear, I think you can just take individual components of [A] and see if it works.
 
Hi mfb,

I've tried that, and unfortunately come up with no solution. I'm wondering of there's some sort of mathemagical trick I've never heard of :)

Thanks
 
What did you get as attempt for
A=
1 0 0
0 0 0
0 0 0

and
A=
0 0 0
1 0 0
0 0 0
?

If both give some corresponding C, it works (based on linearity and symmetry), otherwise it does not work for general matrices A (trivial).
 
mfb said:
If both give some corresponding C, it works (based on linearity and symmetry), otherwise it does not work for general matrices A (trivial).

They don't give the same result, so I guess there is no general solution. Am I correct in interpreting that this also means that any variation of A cannot be solved for? (For example, if A were diagonal).

Thanks
 
The same result? They should not give the same result. Different results are fine.
 
Sorry, to clarify, I meant that inserting your suggested [A] matrices both do not give a valid solution for [C]. I'm concluding that if these simple matrices can't be solved for, then it is correct that there is no solution.

Thanks
 
Okay, I checked it, and there is no solution. It does not work for general matrices A, and I am not sure if there are any solutions apart from the trivial one (A=a*identity matrix).
 

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