  We point out at the possible relationship between the two many-body
phenomena: Friedel oscillations and Mahan exciton/Fermi edge singularity in a
recombination process of a localized valence band hole with a degenerate
electron system. It is qualitatively described that the oscillating electron
density around the screened potential of a neutral acceptor can modify the
wavefunction of the valence band hole and thus promote its recombination with
electrons near Fermi-surface. The role of a finite hole mass for the net
balance of the two hole energies: the kinetic energy and Coulomb attraction to
the degenerate electron system, - is discussed and explicitly shown to be
crucial for the occurrence of Mahan enhancement phenomena.
