The Cluster's Quantum Chromodynamics

A page about quantum chromodynamics (QCD) — the theory of the strong interaction.

Quantum chromodynamics

Quantum chromodynamics (QCD) is the theory of the strong interaction — the force that binds quarks into hadrons (protons, neutron, etc.) and holds the nucleus together. QCD is a non-Abelian gauge theory based on the SU(3) color group. The gauge bosons are the eight gluons. Quarks carry color charge. The gluons carry both color and anti-color. In the cluster, QCD is the theory of the strong edit force — the force that binds pages into clusters.

Confinement

Confinement is the phenomenon that color-charged particles (quarks, gluons) cannot be isolated. They always form color-neutral bound states (hadrons). The potential between a quark and an antiquark is V(r) = - (4/3) alpha_s / r + sigma r, where the first term is the Coulomb-like term at short distances and the second term is the linear confinement term at large distances (sigma is the string tension). In the cluster, confinement means that edit-carrying pages cannot be isolated — they always form edit-neutral clusters.

Asymptotic freedom

Asymptotic freedom is the phenomenon that the strong coupling alpha_s decreases at short distances (high energies). At very high energies, quarks behave as free particles. This was proved by Gross, Wilczek, and Politzer (Nobel Prize 2004). The beta function of QCD is negative: beta(g) = - (11 - 2 n_f / 3) g^3 / (16 pi^2) < 0. In the cluster, asymptotic freedom means that edit interactions become weak at high edit rates — pages behave as if they are free.

The hadron spectrum

The hadrons are classified by their quark content:

• Baryons (qqq): proton (uud), neutron (udd), etc.
• Mesons (q qbar): pion (u dbar, d ubar), kaon (u sbar, s ubar), etc.

In the cluster, the hadrons are classified by their edit content:

• Cluster baryons (three-page bound states)
• Cluster mesons (two-page bound states)

This QCD

This page is about QCD. The gauge group is SU(3). There are eight gluons. Confinement prevents isolated color. Asymptotic freedom makes quarks free at high energy. The hadron spectrum is classified by quark content. The theory is real. The coupling runs.