Luttinger and Hubbard sum rules: are they compatible?

Abstract A so-called Hubbard sum rule determines the weight of a satellite in fermionic single-particle excitations with strong local repulsion ( U → ∞). Together with the Luttinger sum rule, this imposes two different energy scales on the remaining finite excitations. In the Hubbard chain, this has been identified microscopically as being due to a separation of spin and charge.