  We use the Bethe Ansatz solution for the one dimensional Hubbard model with
open boundary conditions and applied boundary fields to study the spectrum of
bound states at the boundary. Depending on the strength of the boundary
potentials one finds that the true ground state contains a single charge or,
for boundary potentials comparable to the Hubbard interaction, a pair of
electrons in a bound state. If these are left unoccupied one finds holon and
spinon bound states. We compute the finite size corrections to the low lying
energies in this system and use the predictions of boundary conformal field
theory to study the exponents related to the orthogonality catastrophe.
