Friday, June 8, 2018

A foolish unified field theory using E8

Someone asked me about this SciAm article:
A Geometric Theory of Everything
Deep down, the particles and forces of the universe are a manifestation of exquisite geometry
A. Garrett Lisi, James Owen Weatherall
December 1, 2010

This quest for unification is driven by practical, philosophical and aesthetic considerations. When successful, merging theories clarifies our understanding of the universe and leads us to discover things we might otherwise never have suspected. Much of the activity in experimental particle physics today, at accelerators such as the Large Hadron Collider at CERN near Geneva, involves a search for novel phenomena predicted by the unified electroweak theory. In addition to predicting new physical effects, a unified theory provides a more aesthetically satisfying picture of how our universe operates. Many physicists share an intuition that, at the deepest level, all physical phenomena match the patterns of some beautiful mathematical structure.

The current best theory of nongravitational forces — the electromagnetic, weak and strong nuclear force — was largely completed by the 1970s and has become familiar as the Standard Model of particle physics. Mathematically, the theory describes these forces and particles as the dynamics of elegant geometric objects called Lie groups and fiber bundles. It is, however, somewhat of a patchwork; a separate geometric object governs each force. Over the years physicists have proposed various Grand Unified Theories, or GUTs, in which a single geometric object would explain all these forces, but no one yet knows which, if any, of these theories is true.

This article is a good example of why I wrote a book on How Einstein Ruined Physics.

The paper does not solve any physical or mathematical problems. It does not explain any experiments. The only thing going for it is a philosophical belief in unification, which is essentially the opposite of reductionism.

In science, reductionism is a good thing, not unification. The Standard Model reduces the 100s of known particles to a 12-parameter Lie group. The philosophy behind these grand unified models is that this was too much reductionism, and we should use a much larger group that does not separate the forces. The above paper uses a 248-parameter group. That means at least 236 more particles than have ever been seen in nature.

The term "simple" in the title does not mean it is a simple model. It means that it uses a mathematical group that is simple in the sense of not being reducible to smaller groups.

Got that? We have a 12-parameter model that matches experiments perfectly, and that allows the fundamental forces to be understood as strong, weak, electromagnetic, and gravity. Lisi and Weatherall say that it is philosophically desirable to trade that for a 248-parameter model that does not match any experiments, but which is supposed to be better because it does not allow treating the fundamental forces separately.

I believe this entire line of research into unified field theories to be wrong-headed. Reductionism is what makes the Standard Model and other good theories great, and not a bad thing. The unified field theorists hate the Standard Model for the same reasons that made it so successful.

These researchers are widely believed to be crackpots, but somehow they got an article in Scientific American. That magazine has really gone downhill.

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