Why Does Index Position in Kronecker Delta and Tensors Not Always Matter?

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In summary, the kroenecker delta has one upper and one lower index and for a 2 index tensor, there are 2 slots for each index. The left or right slot index position does not matter due to the definition of symmetric tensors. The order in which the vector spaces and their duals are chosen is important in defining tensors, especially for a metric manifold. In electrodynamics, the mixed components of the field tensor can have different values depending on the chosen index order.
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helpcometk
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Homework Statement


kroenecker delta has one upper and one lower index. except from uppper index and lower index,we have 2 slots for the upper index and 2 slots for the lower index(for a 2 index tensor).
Why krenecker delta left or right slot index position doesn't matters?
Also why 2 two index tensors may not be equal because of the peculiarity of left and right slot index position?


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  • #2
helpcometk said:
Why krenecker delta left or right slot index position doesn't matters?

That's just because of the definition. Tensors that behave like this are called symmetric.

helpcometk said:
Also why 2 two index tensors may not be equal because of the peculiarity of left and right slot index position?

I don't understand what this question means.
 
  • #3
Because of the general definition of a tensor as a multilinear mapping, the order in which the vector spaces and their duals are chosen really matters, especially when the bundle of tensors is defined for a metric manifold (as is the case in relativity).

You will study electrodynamics and discover that the mixed components of the field tensor are all different, that is

[tex] F_{\mu}^{~~\nu} \neq F^{\nu}_{~~\mu} [/tex]

for arbitrary index values.
 

FAQ: Why Does Index Position in Kronecker Delta and Tensors Not Always Matter?

What is the Kroenecker delta δ?

The Kroenecker delta δ, also known as the Kronecker delta or Kronecker symbol, is a mathematical function represented by the Greek letter δ. It is defined as 1 when the two input variables are equal and 0 otherwise.

What is the purpose of the Kroenecker delta δ?

The Kroenecker delta δ is commonly used in mathematics, physics, and engineering to represent the identity function, which has a value of 1 when the input variables are equal and 0 otherwise. It is also used to define the Kronecker product and to denote a discrete distribution.

How is the Kroenecker delta δ written in mathematical notation?

The Kroenecker delta δ is typically written as δij, where i and j are the two input variables. It can also be written using the Iverson bracket notation as [i = j].

What is the relationship between the Kroenecker delta δ and the Dirac delta function?

Although they have similar names, the Kroenecker delta δ and the Dirac delta function are distinct mathematical functions. The Kroenecker delta δ is a discrete function defined on a finite set of inputs, while the Dirac delta function is a continuous function defined on the real number line.

Can the Kroenecker delta δ be used in vector and matrix operations?

Yes, the Kroenecker delta δ can be used in vector and matrix operations. It is often used to define the Kronecker product, which is a way of combining two matrices to create a larger matrix. It can also be used in operations such as matrix multiplication and addition.

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