Recently the authors proposed two boson approximations to describe the creation of electron-hole pair excitations by a localized time-dependent perturbation. These boson approximations were shown to be exact in certain limiting cases. In this paper the authors compare the results in these approximations with exact calculations where the electrons are treated as fermions. The show that the validity of the approximations is broader than had earlier been proven.
 

Physical Review B, 25 2503-13, 1982.