triqs.operators.util.U_matrix.transform_U_matrix

triqs.operators.util.U_matrix.transform_U_matrix(U_matrix, T)

Transform a four-index interaction matrix into another basis.

The transformation matrix \(T\) is defined such that new creation operators \(\hat{b}^\dagger\) are related to the old ones \(\hat{c}^\dagger\) as

\[\hat{b}_{i \sigma}^\dagger = \sum_j T_{ij} \hat{c}^\dagger_{j \sigma}.\]

Parameters:

U_matrixnumpy.ndarray

The four-index interaction matrix in the original basis.

Tnumpy.ndarray

Transformation matrix for the basis change.

Returns:

numpy.ndarray

The four-index interaction matrix in the new basis.