# triqs.operators.util.observables.N_op

triqs.operators.util.observables.N_op(spin_names, orb_names, off_diag=None, map_operator_structure=None)[source]

Create an operator of the total number of particles.

$\hat N = \sum_{i\sigma} a_{i\sigma}^\dagger a_{i\sigma}.$
Parameters: spin_names (list of strings) – Names of the spins, e.g. [‘up’,’down’]. orb_names (list of strings or int) – Names of the orbitals, e.g. [0,1,2] or [‘t2g’,’eg’]. off_diag (boolean) – Do we have (orbital) off-diagonal elements? If yes, the operators and blocks are denoted by (‘spin’, ‘orbital’), otherwise by (‘spin_orbital’,0). map_operator_structure (dict) – Mapping of names of GF blocks names from one convention to another, e.g. {(‘up’, 0): (‘up_0’, 0), (‘down’, 0): (‘down_0’,0)}. If provided, the operators and blocks are denoted by the mapping of ('spin', 'orbital'). N – The total number of particles. Operator