double dot A:B between two tensors
Description
\[ (A:B)_{i_1,\ldots,j_n,j_1,\ldots,j_m} = \sum_{k,l} A_{i_1,\ldots,i_n,k,l} B_{k,l,j_1,\ldots,j_m} \]
double dot A:B between two tensors
\[ (A:B)_{i_1,\ldots,j_n,j_1,\ldots,j_m} = \sum_{k,l} A_{i_1,\ldots,i_n,k,l} B_{k,l,j_1,\ldots,j_m} \]