[ALPS-users] question about fermion model

Hi,all I am always wondering if I defined the quantum numbers of the fermion site basis in the following way, would there be a negative Ndown number (for example, with N=0, Nup=1)? <QUANTUMNUMBER name="N" min="0" max="2"/> <QUANTUMNUMBER name="Nup" min="0" max="1"/> <QUANTUMNUMBER name="Ndown" min="N-Nup" max="N-Nup"/> Bo-Nan -- Stay foolish,Stay hungry.