  The doping dependence of the superconducting state for the 2D one-band
Hubbard Hamiltonian is determined. By using an Eliashberg-type theory, we find
that the gap function $\Delta_{\bf k}$ has a $d_{x^2-y^2}$ symmetry in momentum
space and T$_c$ becomes maximal for $13 \; \%$ doping. Since we determine the
dynamical excitations directly from real frequency axis calculations, we obtain
new structures in the angular resolved density of states related to the
occurrence of {\it shadow states} below T$_c$. Explaining the anomalous
behavior of photoemission and tunneling experiments in the cuprates, we find a
strong interplay between $d$-wave superconductivity and dynamical spin
fluctuations.
