Study of the interaction between two electrons in the single band Hubbard model

Exact spectrum for n electrons in the single band Hubbard model

“…(27) Now we are able to derive the spectrum for H* (and thus for H,,,): the possible values for q are given in (24), those for A4 in (21), with A = 0. Combination of the possibilities, together with the constraint (27) gives us all possible eigenvalues.…”