Proving Tensor Commutation: T^abc S_b vs S_b T^abc

In summary, a tensor is a mathematical object used to describe relationships between coordinate systems and physical quantities. Commutation refers to switching the order of mathematical operations, which is important in proving tensor commutation. T^abc S_b vs S_b T^abc is a notation for comparing the commutation of two tensors, and to prove commutation, we can use the properties of tensors and the Einstein summation convention.
  • #1
Irid
207
1

Homework Statement


How would you show that

[itex] T^{abc}S_{b} = S_{b}T^{abc} [/itex]

but

[itex] T^{abc} S_{bd} \neq S_{bd} T^{abc} [/itex]

in general?

The Attempt at a Solution


If I write out the sums explicitly, they appear totally the same to me. Any hints or ideas please?
 
Physics news on Phys.org
  • #2
You must be joking, right ? If T and S are commutative variables (Grassmann parity =1), then it doesn't matter in which order you write those two sums.
 

1. What is a tensor?

A tensor is a mathematical object that describes the relationships between different coordinate systems. In physics, tensors are used to describe physical quantities such as velocity, force, and stress.

2. What is commutation?

Commutation is the act of switching the order of two mathematical operations. In the context of tensors, it refers to the order in which indices are written.

3. Why is commutation important in proving tensor commutation?

Commutation is important in proving tensor commutation because it allows us to test whether two tensors are equal. If the order of indices can be switched without changing the result, then the tensors are said to commute.

4. What does T^abc S_b vs S_b T^abc mean?

T^abc S_b vs S_b T^abc refers to the commutation of two tensors, T and S. The notation T^abc indicates a tensor with three indices (a, b, and c), while S_b indicates a tensor with one index (b). The vs indicates the order in which the tensors are written.

5. How do we prove tensor commutation in the case of T^abc S_b vs S_b T^abc?

To prove tensor commutation in this case, we can use the properties of tensors to rearrange the indices and show that the two tensors are equal. This can involve using the commutative property of addition and multiplication, as well as the fact that repeated indices can be summed over. Additionally, we can use the Einstein summation convention to simplify notation.

Similar threads

  • Advanced Physics Homework Help
Replies
1
Views
2K
  • Advanced Physics Homework Help
Replies
1
Views
3K
  • Advanced Physics Homework Help
Replies
1
Views
2K
Replies
1
Views
943
  • Advanced Physics Homework Help
Replies
3
Views
1K
  • Advanced Physics Homework Help
Replies
1
Views
1K
  • Advanced Physics Homework Help
Replies
8
Views
2K
  • Advanced Physics Homework Help
Replies
1
Views
1K
  • Advanced Physics Homework Help
Replies
1
Views
1K
  • Advanced Physics Homework Help
Replies
3
Views
2K
Back
Top