The meson spectrum of large-N QCD

QCD is the quantum field theory of the strong interactions.  It is
based on an SU(N) gauge symmetry with the number of colours N=3,
coupled to fermions in the fundamental representations.  In the limit
of infinite N this theory simplifies. For instance all physical
amplitudes are given by a subset of only planar Feynman
diagrams. Moreover, keeping the number of fermion flavours fixed (the
so-called 't Hooft limit), the effect of sea quarks can be neglected,
reducing QCD to a quenched but unitary model. In this limit the
spectrum consists of stable glueballs and mesons.

Nevertheless this limit is still non-perturbative and far from
trivial.  Phenomenologically, it is a good starting point to
investigations of strong decays, e.g., within the framework of
effective field theories.  From the theoretical side, the large-N
limit of strongly coupled (SUSY-)QCD is conjectured to be dual to
classical supergravity in an anti-de-Sitter background (AdS/QCD
correspondence), allowing for non-perturbative calculations,
preserving the rotational symmetry.

I will summarize recent results from our lattice simulations of the
meson spectrum and decay constants in the large-N limit of QCD and
compare these to real world QCD as well as to phenomenological and
string theory expectations.