ffsim.contract.contract_one_body¶ ffsim.contract.contract_one_body(vec, mat, norb, nelec)[source]¶ Contract a one-body tensor with a vector. A one-body tensor has the form \[\sum_{ij} M_{ij} a^\dagger_i a_j\] where \(M\) is a complex-valued matrix. Parameters: mat (ndarray) – The one-body tensor. norb (int) – The number of spatial orbitals. nelec (tuple[int, int]) – The number of alpha and beta electrons. Return type: ndarray Returns: A LinearOperator that implements the action of the one-body tensor.