The theory of everything

There seems to be two types of high energy physicists, those that work in string theory and those that deride it. The main criticism of string theory is that it cannot generate predictions that are testable with current or even near future experiments. Thus it is really a field of mathematics or philosophy. However, both sides seem to agree that a search for a fundamental theory resides at extremely high energies.

 

Those of us working at eV energy scales, have a very different picture. Philip Anderson probably was the first to voice this alternative view in his famous article “More is Different” (Science 177:393-396, 1971). In that article he noted that each energy scale has its own organizing principles and fundamental laws. Hence, chemistry is not just applied physics, biology is not applied chemistry and psychology is not simply applied biology. Each of these disciplines must be studied in their own right.

 

On this point, I think most high energy physicists just don’t get it. I saw a talk many years ago by Erich Vogt, the then director of the Canadian cyclotron TRIUMF, who started his seminar by outlining the 6 steps or so it takes to construct a cow. He started with quarks and built up the complexity step by step until he got to molecules. After that he said you just combine them and make a cow. I thought that perfectly typified the attitude of some particle physicists who feel that anything bigger than an atom is just quantum mechanics and thus it is just a matter of working out the details. Anderson pointed out that knowing the so-called fundamental laws wouldn’t tell us how a magnet works. Spontaneous symmetry breaking is more important to magnetism than quantum mechanics or any other underlying theory.

 

The aura of high energy physics really dimished for me when I learned statistical mechanics and the renormalization group. Here I found that microscopic interactions may not matter at all. When you go to a large enough scale only gross properties like how many dimensions and symmetries determine the properties of a system. As you go to larger and larger scales, the parameters of the system “flow” in parameter space and eventually converge to a fixed point. Thus, it doesn’t matter what the initial condition was, just the location of the fixed point. I think a fixed point theorem is as fundamental a law as any other. Perhaps someday, string theorists will find that there isn’t a unique theory. A whole family of theories would be consistent with our universe and that would be perfectly fine by me.