Ab initio calculation of the optical model

We explore the effects of short-range correlations in nuclei for positive and negative energies starting from a microscopically generated irreducible self-energy. This approach is an attempt to develop an optical potential obtained from a realistic nucleon-nucleon interaction. In this first study we use a CD Bonn self-energy obtained for $^{40}$Ca. Our results are compared with the ones found using the dispersive optical model (DOM) and with experimental data available for $^{40}$Ca. Finally we outline further necessary developments to obtain a purely {\it ab initio} optical potential that can reproduce experimental data.