Quick question, index notation, alternating tensor.

Therefore, when you substitute these values into the expression, you get -ε_{0123} = -1*1*1*1*1 = -1, which shows that ε^{0123}=-1.
  • #1
binbagsss
1,305
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Q) I am using index notation to show that ε[itex]^{0123}[/itex]=-1 given that ε[itex]_{0123}[/itex]=1.

The soluton is:

ε[itex]^{0123}[/itex]=g[itex]^{00}[/itex]g[itex]^{11}[/itex]g[itex]^{22}[/itex]g[itex]^{33}[/itex]ε[itex]_{0123}[/itex]=-ε[itex]_{0123}[/itex]

where g[itex]_{\alpha\beta}[/itex] is the metric tensor.

I am struggling to understand the last equality.

Many thanks for any assistance.
 
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  • #2
binbagsss said:
Q) I am using index notation to show that ε[itex]^{0123}[/itex]=-1 given that ε[itex]_{0123}[/itex]=1.

The soluton is:

ε[itex]^{0123}[/itex]=g[itex]^{00}[/itex]g[itex]^{11}[/itex]g[itex]^{22}[/itex]g[itex]^{33}[/itex]ε[itex]_{0123}[/itex]=-ε[itex]_{0123}[/itex]

where g[itex]_{\alpha\beta}[/itex] is the metric tensor.

I am struggling to understand the last equality.

Many thanks for any assistance.

Look up the definition of the metric tensor you are using and insert the values of the g components.
 
  • #3
If you are using the standard metric tensor for relativity then [itex]g^{11}= g^{22}= g{33}= -1[/itex] while [itex]g^{00}= 1[/itex].
 

FAQ: Quick question, index notation, alternating tensor.

What is quick question in index notation?

Quick question refers to a specific type of mathematical notation used to represent tensors, which are multidimensional arrays of numbers. In this notation, the indices (subscripts) of the tensor are written in a specific order to indicate the dimensions of the array.

What does the index notation represent?

The index notation represents the components of a tensor, which can be thought of as a generalization of vectors and matrices to higher dimensions. The indices indicate the position of each element in the array.

How is index notation used in physics?

In physics, index notation is used to simplify and generalize vector and tensor calculations. It allows for concise and efficient representation of equations and simplifies the process of solving complex problems involving multiple dimensions and variables.

What is an alternating tensor?

An alternating tensor is a special type of tensor that changes sign when the indices are switched. This property makes it useful for representing cross products and other vector operations in index notation.

How is index notation related to Einstein's summation convention?

Einstein's summation convention is a shorthand notation for representing repeated indices in tensor equations. It is closely related to index notation, as it allows for more compact and simplified representation of equations involving tensors.

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