  We present a new algorithm to analytically continue the self-energy of
quantum many-body systems from Matsubara frequencies to the real axis. The
method allows straightforward, unambiguous computation of electronic spectra
for lattice models of strongly correlated systems from self-energy data that
has been collected with state-of-the are continuous time solvers within
dynamical mean field simulations. Using well-known analytical properties of the
self-energy, the analytic continuation is cast into a constrained minimization
problem that can be formulated as a quadratic programmable optimization with
linear constraints. The algorithm is validated against exactly solvable finite
size problems, showing that all features of the spectral function near the Femi
level are very well reproduced and coarse features are reproduced for all
energies. The method is applied to two well known lattice problems, the
two-dimensional Hubbard model at half filling where the momentum dependence of
the gap formation is studied, as well as a multi-band model of NiO, for which
the spectral function can be directly compared to experiment. Agreement with
results published results is very good.
