Question

Explain the process of contraction of tensors. Show that a ij a^ ij = delta j ^ i .​

Answer 1

Answer:

The contraction of a single mixed tensor occurs when a pair of literal indices (one a subscript, the other a superscript) of the tensor are set equal to each other and summed over. In the Einstein notation this summation is built into the notation. The result is another tensor with order reduced by 2.