What is QCD? – More technically…
QCD is a non-Abelian Gauge Theory.
The gauge group is SU(3).
The Quarks carry the fundamental
representation 3.
The Gluons, which transmit the forces between
quarks, carry the adjoint representation 8.
3 has triality, 8 has no triality.
The theory has defied analytical results despite
the best efforts for more than 25 years.
It is an outstanding problem of theoretical
physics.