## Should we laugh?

Today on arxiv another paper by Oliveira and Silva is appeared (see here). These authors are well-known in the community for being the only one to have seen the gluon propagator bending toward zero in four dimensions being completely at odds with the rest of lattice computations (see here). They used asymmetric lattices. On their papers you will see just a single point in the computed propagator that bends. But maybe, the most shocking one is their paper where exponents of Yang-Mills theory are computed (see here). Here the results are even more striking: They are compatible with a scenario completely at odds with the rest of lattice computations on huge lattices. We would like to remember here that huge lattices arrived at $(27fm)^4$ (see here) and now there is no more interest to increase volumes. So, we have here two researchers, just two, that have such a serious evidence against the evidence! Should we laugh?

I think that the paper they presented today is absolutely unique. They show that there are differences in the SU(2) and SU(3) gluon propagators so that the latter goes to zero and the former does not! This means that the gluon propagator should depend on the gauge group. We just note that the scenario these authors describe is not perfectly coincident with the one emerging from truncation of Dyson-Schwinger equations but is similar to. Indeed, people working with Dyson-Scwinger equations do not see any of such a dependence. This should have given a serious hint at these authors that their conclusions are not correct.

This is the moment to understand. The scenario is set by lattice computations and this is plain evidence to use to trace a boundary between right and wrong. We need good ideas to lead us and not prejudices.

Update: My colleague Terry Goldman at LANL pointed me out that I was too hard in this post against the work of Oliveira and Silva. I have appreciated Terry’s criticism and so I apologize to whoever felt bad by this post.

### 4 Responses to Should we laugh?

1. Orlando Oliveira says:

Dear Frasca, I think that before you make comments on others people work you should read them carefully and think. By the way, who are you to make comment so freely on others people. Maybe you should try to read critically your on works and post some comments.

2. mfrasca says:

Dear Dr. Oliveira,

I have apologized about in the post. It was my mistake. Generally, I avoid to do this as a blog is open to such a wide audience to be devastating and I am new to this kind of communication media. Anyhow, I was asked to apologize and I did it also for you and Dr. Silva as you can see.

Marco

3. Orlando Oliveira says:

Dear Marco, will not discuss your comments but would like to call your attention to the following: i) the title has a question mark; ii) we use symmetric lattices and asymmetric lattices; iii) the analysis is a repetition of the Cucchieri-Mendes analysis but for SU(3) – we refuse to change our data just to agree with someone’s result; iv) if you prefer Cucchieri-Mendes results for SU(2), them Zwanziger 1991 work, which says that D(0) = 0 in the infinite volume, must be wrong(?); v) what is the problem of SU(2) not being equal to SU(3)? My work with Cucchieri, Mendes and Silva say that for q > 1 GeV uthey are equal. Can tell you there the data for lower moment SEEMS to point to some differences. vi) On the lattice the finite volume effects are not understood and they change, they should change, the IR propagator. The final comments in our “unique article”, suggest that maybe the differences came from different finite volume effects. Could also comment on the lattice simulations, I mean my simulations and other’s, but don’t think this is the right place.
Orlando

4. mfrasca says:

Dear Orlando,

Yes, I think that the work of Zwanziger contains a mathematical glitch somewhere. I have the following reason to believe in current lattice results by Cucchieri&Mendes, Ilgenfritz&al. and Sternbeck et al.:

1) They are all for very large volumes and give independently the same results $D(0)\neq 0$.

2) Maas showed that these same lattice computations performed in d=1+1 give Zwanziger’s result but we all know from ‘t Hooft work that Yang-Mills in d=1+1 has no dynamics.

You are right. This is not the right place. I will get in touch with you by email.

Marco