Recent Developments of the Bloch-Modified Ladder Theory

One of the possible theoretical approaches for desribing the physics of electron-positron pairs in the inhomogeneous electron gas is the so-called "quasi-free" Bloch-modified ladder theory. Despite the success of this approach, it contains two very serious deficiencies, namely the complete neglect of the Bloch character of the electron and positron scattering states and of the electron-positron interaction potential. In this contribution, the importance of these Bloch effects for the Bloch-modified ladder theory results, especially for the momentum dependence of the positron enhancement in d-band metals, is demonstrated for the first time.