People really interested about this matter should read the preprint by Elias Kiritsis (see here). This paper gives a full account about this matter and is a recollection of conferences’ contributions yielded by the author.

My point of view about this question, as the readers of the blog may know, is that a general technique to strong coupling problems should be preferred to more aimed approaches. This by no means diminishes the value of these works. Another point I have discussed about the spectrum of AdS/QCD is what happens if one takes the lower state at about 1.19, does one recover the ground state seen in lattice QCD for the glueball spectrum as the next state?

The value of this approach relies on a serious possibility to verify, with a low energy theory, a higher level concept connecting gravity and gauge theories. Both sides have something to be earned.

3 Responses to AdS/CFT and QCD

  1. Ervin Goldfain says:

    Hi Marco,

    Thanks for the informative reference and comments. What concerns me is that all AdS/CFT models for infrared QCD introduce additional free parameters and boundary conditions that need to be fixed “by hand” in order to match experimental or lattice data. No genuine derivation from first principles but fitting with numbers that yield consistent numerical results. This makes me skeptical that holographic QCD is on the right track, but I may very well be wrong. What is your take on it?



  2. hermann says:

    Hi Marco.
    I agree, but the argument about Topological susceptibility in reference [31] seems to me to be poor. In effect I’m not sure that the conclusions of this big paper (about 80 pgs) about it, can be used ‘tout court’ like in the paper of Kritsis. What do u think about it?

  3. mfrasca says:

    Dear Ervin,

    My view is that, whatever is the goodness of these models, they are presently unable to clarify the behavior of QCD in the infrared. Rather they should be seen the other way round, as an approach to clarify AdS/CFT conjecture. Indeed, what these results will produce to fit QCD behavior should turn out useful for models having a true AdS/CFT symmetry as supersymmetric ones. In this way they could become a strong support for string theory, if successful.

    Dear hermann,

    Reference [31] is a paper about a known problem of QCD that has been through a lot of analysis for a long time with a lot of contributions coming from notable physicists. It is still an open question. The author of the paper in my post just cites it to retrieve a the definition of topological susceptibility. My take is that, presently, AdS/QCD is not able to face such kind of problems being at the very beginning and with a lot of severe questions to be addressed. I think that people working with AdS/QCD will be already very happy to recover the right spectrum of the theory as this would imply a lot of understanding about this conjectured symmetry.


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