Monday, January 09, 2017

Disappointing composition of top-cited 2016 HEP papers

Stephen Hawking celebrated his 75th birthday yesterday, congratulations! Lots of other websites remind you of the basic facts. He's well-known to the physicists primarily for the Hawking radiation of black holes and related insights about black hole thermodynamics; but also for his and Penrose's singularity theorems and other things. He's also revolutionized the popular physics book market. As Hawking mentioned, he has sold more books about physics than Madonna has about sex.

The experimental counterpart of this statement isn't quite true. We have observed fewer evaporating black holes than Madonna's sex scenes, however, namely zero.

I found it interesting to look at the 2016 data papers on high energy physics that already have over 100 citations according to INSPIRE, the database of particle physics papers. This particular search finds 126 papers right now.

The beginning of the list of the papers looks like "almost everything would be experimental papers". But after a few dozens, you must change your mind. A majority of the papers is about the \(750\GeV\) diphoton excess that was exciting many particle physicists a year ago. Recall that it was announced in December 2015 and before the more than 4-sigma excess seen both by CMS and ATLAS was buried by the new data published in Summer 2016, hundreds of papers – often interesting papers – were written to offer possible explanations of this possible new phenomenon.

Many of these papers rightfully cited their counterparts which is why dozens of them have surpassed the threshold of 100 citations by now. Needless to say, not it looks rather clear that there are no new elementary particles of mass close to \(750\GeV\) – to say the least, no new particles of this mass are as easily visible as we could imagine one year ago.

So this tremendous activity was a kind of a bet on an event that couldn't have been predicted. Those who invested their time and energy have basically lost the bet. The particle isn't there, after all. But just because they lost the bet doesn't mean that the time and energy were completely wasted or that it was torture for the physicists to do the work.

Instead, the physicists were genuinely excited by the chance for a new discovery and when a physicist (or someone else) is excited, the work is much easier. And even though the particle isn't there, the papers have clearly articulated and sharpened the details with which various theoretically intriguing models could explain a similar new effect if one turned out to be real.

But aside from the papers on the \(750\GeV\) diphoton excess, most of the top-cited papers are experimental, indeed. Something like 5 papers in the list are analyses by the LIGO collaboration of their exciting direct detection of the gravitational waves, especially GW150914, which allowed us to hear the Universe. Many physics pundits have identified this discovery as the most important development in physics in 2016 and I would probably agree.

Additional top-cited experimental papers include the new Review of Particle Physics and articles by the teams at the LHC, Fermi (the \({\rm GeV}\) galactic excess is an intriguing topic of one of the papers), and the terrestrial searches for dark matter, especially LUX and XENON. None of these experimental papers has made a clear experimental discovery but that's not necessarily the fault of the experimenters.

Formal theoretical papers – or, almost equivalently, theoretical papers after the diphoton models are subtracted – are rare. One successful paper is about tetraquarks and pentaquarks. I find these QCD bound states rather messy yet boring but they represent serious work on messy and boring topics.

One paper by Strominger and two junior colleagues is about dS/CFT applied to Vasiliev's higher-spin theory. The holographic model living on the "far future" dS boundary includes anticommuting scalars with a symplectic symmetry. I haven't discussed that paper but the degree of detail they may deduce for this dS holographic duality makes the whole work persuasive and intriguing.

Hawking, Perry, Strominger wrote about their "soft hair" solution of the black hole information paradox. I've discussed that paper many times and unfortunately I don't think that the far-reaching conceptual claims are correct and I am convinced that most true quantum gravity experts find them flawed, too.

Maldacena, Shenker, and Stanford have proposed a very interesting general bound on chaos.

Several top-cited papers in the list are older and only got there that they were published in paper journals in 2016. If you think that I should have discussed some paper in the list, or some paper is missing for some undeserved reasons, let me know.

I find it unfortunate that for a few years, there hasn't been a too specific "fad" or concentrated activity in formal theoretical particle physics – string theory etc. – that would make it to such lists. Well, just to be sure, several papers above could be viewed as representatives of the "information in quantum gravity" subindustry but I think that this topic is too broad to be called a "fad". Apparently, there aren't any realistic problems that could be solved – or looming discoveries that could be made – that are eagerly expected by a significant fraction of the world's elite theoretical physicists right now. So I think that if there are some ingenious undergraduate seniors at a university anywhere in the world, they have a much harder time to turn into stars than in other periods of the history of physics.

This negative situation may be partly due to historical coincidences, partly due to the decreased funding of the theorists in recent years, and partly due to the hostility towards theoretical physics that became rather widespread in the same years. I think that it's obvious by now that the jihadists who have fought against string theory and supersymmetry, among related key disciplines, have fought against theoretical physics as a whole – simply because there aren't any solid yet exciting ideas in the field that would be quite independent of string theory – and I think that they have harmed the field, indeed – well, at least sufficiently for them to deserve a severe punishment.

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