Baryonium, tetra-quark state and glue-ball in large N_c QCD

Understand

From the large-N_c QCD point of view, baryonia, tetra-quark states, hybrids, and glueballs are studied.

• The existence of these states is argued for.
• They are constructed from baryons.
• In N_f=1 large N_c QCD, a baryonium is always identical to a glueball with N_c valence gluons.