triqs.operators.util.U_matrix.reduce_4index_to_2index
- triqs.operators.util.U_matrix.reduce_4index_to_2index(U_4index)[source]
Reduce the four-index U matrix to two-index matrices for parallel and anti-parallel spins.
- Parameters:
- U_4indexnumpy.ndarray
The four-index interaction matrix.
- Returns:
- Unumpy.ndarray
The two-index interaction matrix for parallel spins.
- Uprimenumpy.ndarray
The two-index interaction matrix for anti-parallel spins.