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Discussion regarding "Meson Fermion model" name, from question on composite SUSY

+ 0 like - 0 dislike
2641 views

Discussion from this question: http://physicsoverflow.org/22998/supersymmetry-transformations-involve-composite-sector . I judged it off-topic, but OP disagrees. The question is whether the original intention of the 1970s string crowd was to make a supersymmetry between fermionic quarks and mesonic bound states.

asked Aug 30, 2014 in Chat by SchrodingersCatVoter (-10 points) [ revision history ]
edited Aug 31, 2014 by Ron Maimon

2 Answers

+ 1 like - 0 dislike

Thanks to a reference of @40277, I see that in 1974 the supersymmetric string model was still called the "MFM", Meson-Fermion Model, by Sherk and Schwarz, in http://ccdb5fs.kek.jp/cgi-bin/img/allpdf?196800234  Also it was referred as "Fermion Meson dual model" by Corrigan and Olive in 1972, or Brink and Fairlie in 1974, 

answered Aug 30, 2014 by - (255 points) [ no revision ]

MFM simply meant "string with fermions and bosons both", as opposed to "string with only bosons". The bosons in the string are not bound-states of the fermions except in the bootstrap meaning that they are both Regge trajectories, and the fermions can scatter into bosons in the theory and vice-versa, and all the trajectories have soft scattering like bound states. You are asking a much more interesting question about whether you can relate fundamental fermions to composite bosons with a form of supersymmetry, perhaps a new form.

@Ron, I'd say your comment is offtopic, because it refers to a concept in my paper (where the bosonic sector is composite of the fermionic sector) and here the question is only if the bosonic sector can be composite, while remaining agnostic about what the constituents are.

As for my remark, I think that if Schwarz had wanted to call the model "a fermion-boson model", he had done. If he had wanted to call the model "a baryon-meson" model, he had done. That he choosed "meson" and some other guys followed suit, is relevant to the question, as far as we know now that the Dual Model in question was the first motivation for supersymmetry.

The reason for the name is that the string was initially interpreted as a description of hadrons. The names are completely unimportant, the thing is referring to a supersymmetry between internal oscillations of the superstring, and there is also a related supersymmetry between "mesons" and fermions in the full superstring, but this is not a symmetry between physical quarks and physical mesons, rather it is a supersymmetric field theory approximating the low-energy superstring.

The mismatch between the string theory model and the QCD spectrum was one of the reasons people abandoned this approach to the strong interaction in the 1970s, but it is better now. In no case did they make a supersymmetry between fermionic constituents and bosonic bound-states, that's what you want to do. This hasn't been done, and it is interesting to explore if it can be done.

Note that In two papers in 1971, Schwarz uses also the alternative formulation "quark-gluon", that I have cited in some other note.  I can not tell now if he uses some other combination (I expect you will agree that "quark-meson" should be a definitive give-away) but it is clear that during this period they are thinking that the bosonic part is the set of strongly interacting mesons, and on the other hand for the fermionic part they are not sure about identifying it with the baryons.

What we know now about superstring or M-theory is completely irrelevant, the point of the remark is what was known or conjectured in the early seventies.
 

Yes--- there was confusion in the early 1970s, they didn't know how to identify the fermions, whether they should be baryons or not. But they never identify them with quarks, and even if they did, it is irrelevant, because the fermionic content of the superstring does not make the bosonic content as a bound state in any way other than in the traditional bootstrap meaning that the trajectories can merge into other trajectories. It isn't through a traditional force law, at least.

Asking what Schwarz was thinking in the 1970s is interesting, but even if he thought exactly like you, it doesn't matter, this is not a psychology site devoted to studying Schwartz's psychology, it is about the physics, that is, the models themselves.

This is why discussions about names and so on are completely wasting everyone's time.

+ 0 like - 0 dislike

Ron, let me do another off topic remark: I consider the deletion (hidding) of the http://physicsoverflow.org/22998/supersymmetry-transformations-involve-composite-sector?show=23102#c23102 first comment as aggresive. We are going to discuss it here but you have already decided that it was to be deleted of the initial thread? I have not problem on discussing here on the question of naming and meaning of these papers, to avoid cluttering of the main issue, but definitely they are relevant to the topic even without any mention to the names, as they are the historical origins of the subject of particle supersymmetry.

Note that agresive pressure in the main question is against our agreement to delay submission of the paper to the review section. I advanced you that I did not believed that the reception were to be different, you assured me that it was to be better than a review submission, and then you proceed to argue against and finally move to deletion the first comment I do in such questions. I think that if the comment is not restored the previous assurances were completely faked, and then I would ask the moderators to finally decide about the submission for reviews.

EDIT: well, whatever, it is plainly stupid to become infuriated by an action I had bet it was going to happen and that I just let to happen by agreeing to try the questions instead of the review. So I will not tell that you should offer apologies to me, but perhaps you owe some of it to the PO community and refrain to use this trick next time. It could be more useful, and will bring more people to the forum, if you allow reviews and just do a serious criticism there, showing that you have read the paper.

My best wishes for the forum. I will check again after some months.

answered Aug 31, 2014 by - (255 points) [ revision history ]
edited Aug 31, 2014 by -

It might have been aggressive, sorry. Here are all your relevant comments, and the judgement of "on topic" or "off topic" is just to keep the Q&A from getting cluttered with personal or off-topic stuff like all this crap here.

Your question is good, and your comment was probably ok. To make it clear it's on topic, you could have said: "Did Schwarz in 1971 consider the fermionic excitation of the RNS superstring to be identified with quarks and the bosonic excitations with mesons? If so, what would the supersymmetry relations look like between the quarks and the mesons?" Then I would understand why you were asking this. I misjudged, sorry.

Even if the answer to the first part of this question is yes, in 1971, there was no supersymmetry relation between the fermionic and the bosonic sector, that came with GSO in 1976, so it wouldn't have been a suggestion of the type of symmetry that you want. Even if Schwarz suggested exactly your supersymmetry, it doesn't matter, as we don't decide things based on authority, but based on physics. Schwarz could be wrong, as I could, or you, you need to check the models themselves, not what such and so big-shot said.

I explained why your comments are off topic several times, you keep wanting to discuss personalities and names, rather than the content of the physics. The site is designed to talk about physics, not about people.

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