The difference is, QED vacuum contains no electrons, while QCD vacuum contains no quarks.Hi pf, i have been wondering what differentiates QED Vacuum from QCD Vacuum?
Ok then, if it is not zero, what is its value?##\langle N_s \rangle_\text{vac} = \langle\text{vac} | N_s | \text{vac}\rangle \neq 0##
I was cheating a little bit b/c one does not determine <N> but the (flavor-specific) quark condensate; afaik the (ren.-scheme dep.) values are in the range of 300 MeV^{3}; afaik in two-flavor QCD the value can be related to the pion mass and decay constant via the Gell-Mann–Oakes–Renner relation, e.g. in current algebra and chiral perturbation theory; there should be lattice gauge calculations as well.Ok then, if it is not zero, what is its value?