Antisymmetric and symmetric part of a general tensor

In summary, the statement that a general covariant or contravariant tensor of rank n can be separated into its symmetric and antisymmetric parts only holds for the case n=2. For n=3 or more, there is also a leftover part with "mixed" symmetry. This can be confirmed by counting the independent components of the symmetric and antisymmetric parts.
  • #1
center o bass
560
2
I've seen it stated several times that a general covariant or contravariant tensor of rank n can be separated into it's symmetic and antisymmetric parts

[tex] T^{\mu_1 \ldots \mu_n} = T^{[\mu_1 \ldots \mu_n]} + T^{(\mu_1 \ldots \mu_n)}[/tex]

and this is easy to prove for the case n=2, but I don't see how to prove it for a general n. Could anyone help me out?(suspect this has been posted in the wrong forum, but I also suspect that the general relativists can answer this question as good or better than the mathematicians)
 
Physics news on Phys.org
  • #2
You're right, this statement holds only for two indices. For three or more you can separate the totally symmetric part and the totally antisymmetric part, but there's leftovers. This is easy to confirm just by counting up the independent components of the symmetric and antisymmetric parts and seeing that they don't add up to the expected total. We say the leftover part has "mixed" symmetry.
 

1. What is the difference between the antisymmetric and symmetric part of a general tensor?

The symmetric part of a general tensor is the part that remains unchanged under a swap of two indices, while the antisymmetric part changes sign. In other words, the symmetric part is symmetric with respect to index permutations, while the antisymmetric part is antisymmetric.

2. How can the antisymmetric and symmetric parts of a tensor be calculated?

The antisymmetric part of a tensor can be calculated by taking half of the difference between the tensor and its transpose. The symmetric part can be calculated by taking half of the sum of the tensor and its transpose.

3. What is the significance of the antisymmetric and symmetric parts in physics?

In physics, the antisymmetric part of a tensor is often associated with quantities that represent rotations or angular momentum, while the symmetric part is associated with quantities that represent translations or linear momentum.

4. Can a tensor have both symmetric and antisymmetric parts?

No, a tensor cannot have both symmetric and antisymmetric parts. This is because any tensor can be uniquely decomposed into its symmetric and antisymmetric parts.

5. Are the symmetric and antisymmetric parts of a tensor independent of each other?

Yes, the symmetric and antisymmetric parts of a tensor are independent of each other. This means that they can be manipulated separately and do not affect each other's values.

Similar threads

  • Special and General Relativity
Replies
22
Views
2K
  • Special and General Relativity
Replies
5
Views
971
Replies
1
Views
1K
  • Special and General Relativity
Replies
1
Views
664
  • Special and General Relativity
Replies
3
Views
1K
  • Special and General Relativity
Replies
11
Views
1K
  • Special and General Relativity
3
Replies
78
Views
4K
  • Special and General Relativity
Replies
6
Views
3K
  • Special and General Relativity
Replies
33
Views
4K
Replies
2
Views
2K
Back
Top