As pointed out in my recent post (see here), f0(980) can be a glueball and an excited state of 
“The physics of the σ is governed by
the dynamics of the Goldstone bosons: The properties of
the interaction among two pions are relevant… The properties of the resonance f0(980) are also governed by Goldstone
boson dynamics – two kaons in that case.”
This is just the scenario I depicted in my papers. But I was also able to find a very smart paper by Baru, Haidenbauer, Hanhart, Kalashnikova and Kydryavtsev (see here and here) where a proof is given that this resonance has not a quark structure. This is accomplished through an approach devised by Steven Weinberg that applies to unstable particles.
This is a strong support to our scenario that appears consistently built. In turn, this implies that a clear understanding of the very nature of light unflavored scalar mesons is at hand.
The Gauge Connection 
Hello Marco!
There are 2 articles that distub me for 5 years about Glueballs. I really don’t know if they are worth to be taken seriously or not. I am not an expert at all in QCD.
http://arxiv.org/abs/hep-ph/0301089
http://arxiv.org/abs/hep-ph/0209339v3
These guys claim to find the whole spectrum of glueballs by using knot theory. You don’t have to know knot theory, these guys just tells what one needs to know in the article, but I am not sure if I can take them seriously.
I really want to know you opionion.
Cheers.
Daniel de F.
There is another article with a long table showing the energies of several resonances, claimed to be glueballs, and their relation with their supposed knot mass spectrum:
Click to access 0408027v1.pdf
that includes f0(980)
See table I and Fig. I.
It seems to be extremely amazing to be true.
Cheers,
Daniel.
Dear Daniel,
I have read these papers that you have pointed out. I was not aware of these works and I should say that I have to thank you for let me know them. The approach is surely interesting and results are striking. As said in one of these papers, this appears a Bohr-like approach to the glueballs problem.
There is a small question. Some time ago I have read a paper by Coleman proving that there is no classical glueball. The reason is that that solitons or lump solutions do not exist for Yang-Mills theory. Indeed, we can have only nonlinear waves and I have shown this in some other posts. You can find these kind of solutions here
http://arxiv.org/abs/0807.2179
These nonlinear waves already display the typical glueball spectrum that can be seen in QFT.
Anyhow, you can see how successful is such a Bohr-like approach by the right spectrum they get. Very nice indeed.
Marco
I would find it more impressive if there was an obvious correlation between the characteristics of the knot and the quantum numbers of the state. For example, one would prefer to have all the resonances with the same
have knots related to one another.
Marco,
I am sorry for not answaring before. It seems I had a caching problem here in which whenver a tried to reload your page, your answer did not appear, so I gave up coming here 😦
But I see there is a discussion for glueball later. Thanks 🙂