  The weak coupling many-polaron formalism is applied to the case of the
polaronic system consisting of impurities in a Bose-Einstein condensate. This
allows to investigate the groundstate properties and the response of the system
to Bragg spectroscopy. This theory is then applied to the system of
spin-polarized fermionic lithium-6 impurities in a sodium condensate. The Bragg
spectrum reveals a peak which corresponds to the emission of Bogoliubov
excitations. Both ground state properties and the response spectrum show that
the polaronic effect vanishes at large densities. We also look at two
possibilities to define the polaronic effective mass and observe that this
results in a different quantitative behavior if multiple impurities are
involved.
