8 votes
Accepted

Ghosts in QCD Lagrangian

It's conventional to specify the classical Lagrangian, which does not include ghost terms. (Ghosts only contribute at loop level). One reason not to write ghost terms, when one is speaking generically ...
Andrew's user avatar
  • 48.8k
4 votes

Ghosts in QCD Lagrangian

Briefly speaking, OP's Lagrangian density (1) is the un-gauge-fixed original Lagrangian density ${\cal L}_0$ for QCD. ${\cal L}_0$ defines the classical theory. Now let us quantize the theory. In the ...
Qmechanic's user avatar
  • 203k
1 vote

Yang-Mills mass gap caused by gluonballs or because dark matter WIMPs?

There is no reason to believe gluonballs will be different in this respect than any other composite particle; in other words, we have no reason to believe that gluonballs will be dramatically lighter.
Wel Xavier's user avatar
1 vote

How can I calculate action of $\mathfrak{su}(3)$ or other simple algebra ladder operators on "states" from the algebra commutators?

This is actually non-trivial to do in practice. One practical reason is there is no uniform phase convention for various irreps of $su(3)$ (or $su(n)$). In other words, there could be many ...
ZeroTheHero's user avatar
  • 45.5k
1 vote
Accepted

Motivation for the shape of the theta vacua

As boring as this might sound, the simple reason why $\left|\theta \right>$ is the correct vacuum for QCD is because it is an eigenstate of any Hamiltonian which verifies $$ \left<n \right| H \...
Gabriel Ybarra Marcaida's user avatar

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