Fermi-edge singularities in x-ray spectra of strongly correlated fermions

We discuss the problem of x-ray absorption in a D-dimensional system of interacting fermions and, in particular, those features in the x-ray spectra that can be used to discriminate between conventional Fermi liquids and “strange metals.” We find that the x-ray Fermi edge singularities can still be present, although modified, even if the density of states vanishes at the Fermi energy, and that, in general, the relationship between the two appears to be quite subtle