Gell-Mann's Eightfold Way is Good

HC Lee

2020 July 23

My apologies for replying to Sheng-Zu's July 13 email query so late.


I do not fully agree with Alexander Unzicker's video Overhyped Physicists: Why Gell-Mann was not a Genius. Judging by his Wiki page, criticizing high-energy physics is his hobby-horse. I agree with this criticism (by Florian Freistetter) of one of his books: the book was "far from being a reasonable criticism of modern physics. In From Big Bang to Crazy Bang (modern physics) is scolded, grumbled and complained about; physical descriptions alternate with personal attacks on scientists and the criticism of string theory is so exaggerated that, with the best will in the world, it can no longer be taken seriously."

I think here Unzicker commits the same mistake: vicious attacks, some personal, as opposed to serious discussion of science. I my view, there is nothing wrong in Gell-Mann's Eightfold Way: assigning SU(3) symmetry to part of the internal symmetry of quarks. This has consequences and does help scientists to understand, even predict the existence of the spectrum of elementary particles. Connecting aspects of fundamental physics to mathematical structure is what physics is about, and associating algebra with physics is not new. The energy spectra of nuclei are described very well by the algebra of angular momentum, which includes that of nucleons rotating in space, as well their INTERNAL spins (not a motion in space).

Unfortunately, after the success of Gell-Mann, the application of Lie algebra to particle field theory got out of hand. An entire generation of theorists used Lie algebra to build unified field theories based on non-existent particles, and then it got even worse when they built field theories with supersymmetry. As far as I know, as yet none of these theories have had any experimental support.

Unzicker is right when he criticizes some particle physics of arrogance and hubris. It is a mistake to invent terms such as "Theory of Everything" (TOE) and God's Particle (Higgs).

Unzicker's criticism of string theory is, in my view, justified. If nothing else, simply because none of its (actually there are many string theories) predictions can ever be experimentally verified: the energy needed for a particle accelerator to test any of the predictions do is many orders of magnitude higher than anything human will ever be able to reach.

That being said, there is a valid reason why (very clever) people proposed string theory: based on current knowledge, it is the only known path to quantize gravity. Currently, all evidence and tests suggest that both classical gravity and quantum theory are on solid ground. But the two cannot be united, because in four-dimensional space-time, a simple dimensional analysis would show that, in quantized gravity, vacuum polarization would be infinite. Gravity can be quantized in some space-time whose dimension is greater than four. String theory arose from the desire by theorists to quantize gravity and to united it with the other three known fundamental interactions, the electromagnetic interaction that binds nucleons ? proton and neutron ? and electrons the basic elements, the strong interaction that binds quarks to form nucleons and other elementary particles, and the weak interaction that control the burning of stars. There are many possible string theories, the one favored by theorists is one that has supersymmetry and lives in a ten-dimensional space-time.

Unfortunately, as mentioned above, none of crucial predictions of any string theory can be experimentally verified in the foreseeable future. Perhaps better understandings of gravity and quantum theory would emerge in the future that could lead to a testable quantized gravity in four-dimensional space-time.

For reasons given above, I am opposed to China building new particle accelerators. It will not only be a huge waste of resources; it will also be a great misuse of China's bright minds. In the last 30 years, after phenomenal expenditures in money and manpower, the ONLY new experimental verification of the standard model is the observation of the Higgs particle.


© HC Lee, July 23, 2021, Taoyuan, Taiwan