Even the GW method cannot reproduce this spectrum. The GW method gives only one peak at ε 0 +U/2, in line with the fact that this method describes the paramagnetic phase of transitionmetal oxides as metallic. This happens because the GW method treats the charge/spin density as a classical charge distribution, with half an electron with spin up and half an electron with spin down on each atom that respond to the additional electron or hole added to the system in a photoemission experiment. If one considers instead the spin-symmetry broken state |Ψ 0 = | ↑ ↓ (or, equivalently, | ↓ ↑ ), which is also an eigenstate of the system in this limit, then the GW method gives the correct spectral function. In this case, the electrons have fixed positions and one does not need to consider explicitly the correlation between two particles. One may therefore think that there is little correlation in this state. In reality, the system is correlated, but part of the correlation is included in the symmetry breaking.