Zitat:
Zitat von lkcl
...
so my question in effect is: would it be *reasonable* to assume that the formula (1.7) would *also* represent... a quark (generation 0), as well as a pion (generation 2)?
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I think that you have got this wrong: (1.7) in the paper describes a so-called gauge transformation which acts on the gauge fields of QCD ("gluons"). There are no quark fields in this equation. Quarks are represented by spinors, see eq. (1.6); the psi there is a quark field.
Zitat:
Zitat von lkcl
if the above is not obvious (that pions and gluons are the same thing), look further in that PDf at Figure 1.2, it even *says* in the paragraph above that there are eight "gluons". well, there are eight *pions*
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QCD is a theory of gluons and quarks, it doesn't know about pions.
It's true that pions and gluons arrange in octets. However, the background is completely different: while gluons are octets in the space of the color quantum number ("red", "green", "blue"), pions on the other hand are octets in flavor space (flavors are "up", "down", "strange"). There is no relation between these representations.
Representations of baryons in flavor space are for instance described here:
http://www.ks.uiuc.edu/Services/Clas..._PDF/chp12.pdf