Self energy zeroth-order degenerate states

B The dynamic particle-hole self energy C The zeroth-order degenerate states D First order self energy... 

We will see later that these states, which we call /f-states, are in zeroth-order degenerate to the y-states and contribute to the dynamic part of the self energy. The fourth component of the primary states contributes in the... 

Concluding, we have shown that the present approximation to the matrix leads to the RPA. In terms of the self energy, the present approach consists of a first order static part of the self energy like in the FOSEP approximation and additionally to that part of the dynamic self energy comprising the AT-states which are in zeroth order degenerate to parts of the primary (static) block. 

The zeroth order degeneracy of K and T-states is lifted in the spectral representation of the fully interacting Green s function. The exact eigenstates decouple to yield A -particle states in the second component and tensor products of W — 1 and N -L 1-particle states in the third component. We will come back to discuss the meaning of the degenerate states A >) in connection with the lowest order of the static self energy S oo) in Sec. V. 

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