  We show that a strongly renormalized band of polaronic quasiparticle
excitations is induced at the Fermi level of an interacting many-electron
system on increasing the coupling of the electrons to local phonons. We give
results for the local density of states at zero temperature both for the
electrons and phonons. The polaronic quasiparticles satisfy Luttinger's theorem
for all regimes considered, and their dispersion shows a kink similar to that
observed experimentally in copper oxides. We calculate the quasiparticle weight
factor $z$ and deduce the local effective inter-quasiparticle interaction
$\tilde U$. Our calculations are based on the dynamical mean field theory and
the numerical renormalization group for the hole-doped Holstein-Hubbard model
and large on-site repulsion.
