Consider the Lehman representation,
the PPA assumes that all the weight is given by a single excitation at the plasmon-pole frequency:
This approximation is justified since it has been observed that in general the Fourier components are characterized by a strong peak at the plasmon pole frequency. The variables in the calculations are analogous to those for the response function ( Xd ): QpntsR decides the momenta at which the response/screening is calculated; NGsBlk decides the response/screening block-size; BndsRn governes the band summation of the non-interacting response function; EhEngy selects the energy of the hole-pairs in the electron-hole Green's function. In the PPA yambo considers a casual Green's function.
where we understood all indexes for simplicity. From that one obtains:
The PPA imaginary energy Eo can be changed with PPAPnt .