Editing Faddeev–Popov ghost (section)

==Spin–statistics relation violated==
The Faddeev–Popov ghosts violate the [[Spin–statistics theorem|spin–statistics relation]], which is another reason why they are often regarded as "non-physical" particles.

For example, in [[Yang–Mills theory|Yang–Mills theories]] (such as [[quantum chromodynamics]]) the ghosts are [[complex number|complex]] [[scalar field theory|scalar fields]] ([[Spin (physics)|spin]] 0), but they [[anticommutativity|anti-commute]] (like [[fermions]]).

In general, [[anticommutativity|anti-commuting]] ghosts are associated with [[boson]]ic symmetries, while [[commutativity|commuting]] ghosts are associated with [[fermion]]ic symmetries.