In the first days of July 1997, after a long driving effort, crossing all of Europe to come to a meeting in Peñiscola, Vladimir Gribov fell fatally sick and he passed away one month later. His paper "QCD at large and short distances" was uploaded posthumously to arXiv:hep-ph/9708424 and, in edited version, to arXiv:hep-ph/9807224 one year later. Still a remaining write-up, "The theory of quark confinement", was collected, edited and uploaded later to arXiv:hep-ph/9902279.
I guess that I am asking for some general review of these articles, but I am particularly intrigued by the conclusion as it is exposed in the introduction to the first one (bold emphasis is mine).
"The conditions for axial current conservation of ﬂavour non-singlet
currents (in the limit of zero bare quark masses) require that eight
Goldstone bosons (the pseudo-scalar octet) have to be regarded as
elementary objects with couplings deﬁned by Ward identities."
"... the ﬂavour singlet pseudoscalar η′ is a "normal bound state of
qq¯ without a point-like structure"
How serious is this elementary status? For instance, in order to do calculations of electroweak interaction, should the bosons in the octet be considered as point particles, say in a Lagrangian? Does it imply that the QCD string, at low energy at least, is point-like?
And, does it happen the same for the colored state having two quarks? (What I mean here is the following: the color-neutral states have been produced from the decomposition $3 \times \bar 3 = 8 + 1$ of SU(3) flavour, joining a quark and an antiquark. Similarly, we could use QCD to join two quarks, and then SU(3) flavour should decompose as $3 \times 3 = 6 + 3 $) Is the flavour sextet "pointlike"? And the triplet then, is it still a "normal bound state"?
I expect the argument does not depend of the number of flavours, so the same mechanism for SU(5) flavour should produce a point-like color-neutral 24 and, if the answer to the previous question is yes, a point-like colored 15. Is it so?
Let me note that most work on diquarks concludes that only the antisymmetric flavour triplet, not the sextet, is bound by a QCD string --e.g., measured as $\sqrt 3/2$ times the meson string here in PRL 97, 222002 (2006)--.
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