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Given tensors and their indices, sum over repeated indices
ResourceFunction["EinsteinSummation"][indices,tensors] sums over repeated indices of the tensors. | |
ResourceFunction["EinsteinSummation"][indices→out,tensors] transposes the output if necessary so that the output tensor indices match out. |
Two explicit matrices:
In[1]:= |
Contract the second indices of the two matrices:
In[2]:= |
Out[2]= |
Check:
In[3]:= |
Out[3]= |
Perform the contraction AikMjk for symbolic tensors A and M:
In[4]:= |
Out[4]= |
Perform the contraction AikMjk and transpose the output:
In[5]:= |
Out[5]= |
The indices can be any expression:
In[6]:= |
Out[6]= |
The number of index specifications must match the number of tensors:
In[7]:= |
Out[7]= |
If $Assumptions is used to define symbolic tensors, the number of indices must match the tensor rank:
In[8]:= |
Out[9]= |
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