Take the tour ×  At one point, I decided to make friends with
the low-lying spectrum of QCD. By this I do not mean the
symmetry numbers (the "quark content"), but the actual dynamics,
some insight.  The pions are the sloshing of the up-down
condensate, and the other pseudoscalars by extending to
strangeness. Their couplings are by soft-particle theorems. The
eta-prime is their frustrated friend, weighed down by the
instanton fluid. The rho and omega are the gauge fields for
flavor SU(2), and A1(1260) gauges the axial SU(2), and they have
KaluzaKlein-like echoes at higher energies, these can decay into
the appropriate "charged" hadrons with couplings that depend on
the flavor symmetry multiplet. The proton and the neutron are
the topological defects. That accounts for everything up to 1300
but a few scalars and the b1.   On the other hand, there is
nothing in AdS/QCD which should correspond to the sigma/f0(600),
or (what seems to be) its strange counterpart f0(980). While
looking around, I found this discussio