# Verifying that a tensor is isotropic

1. Oct 6, 2011

### evlyn

I'm supposed to verify that this fourth-rank tensor is isotropic assuming cartesian coordinates: [A]_{}[/ijkl]=[δ]_{}[/kl][δ_{}[/kl]

from what I gathered being isotropic means that it stays the same no matter what the rotation is

I have no clue how to even start this problem or what I am looking at.

2. Oct 6, 2011

### HallsofIvy

Staff Emeritus
I recommend that, instead of saying what you "gather" isotropic means, you write out the specific definition. You use the precise words of definitions in mathematics proofs.

3. Oct 6, 2011

### evlyn

I'm not even sure how to go about doing that. I am taking math methods but have been out of school for a while and just trying to relearn things and I never took a proof class before. My book does not give any definition other than the one in English but there is no math that I can find that has the definition. Is there someplace I could go to find the definition.

4. Oct 7, 2011

### evlyn

So I figured out that I need to rotate the tensor and from there show that it is the same in the new rotation. So if I have A_ijkl=(δ_ij)(δ_kl) In order to transform it I'm not really sure how to proceed.

Last edited: Oct 7, 2011
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