A quick history from Dirac to Superstrings

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Posted by DickT on December 19, 2002 at 08:07:26:

In Reply to: Re: Question about Paul Dirac(The existance of the Positron) posted by sol on December 18, 2002 at 15:24:19:

sol,

Let's start the history with Dirac's theory of the electron. This post goes together with my other one on the prehistory of strings.

Dirac made the ony perfect quantum theory. He got it all together, spin, quantum and relativity, each one supporting/deriving from the other two. And it had a decade of successful predictions.

But in 1948 Lamb and Retherford showed that the spectrum of microwaves had a line shift that was not predicted by Dirac. This came to be called the Lamb shift, and the race was on to explain it. People had been working with quantum field theories since the 1930s, and encountering the famous infinitiess. Four people now showed ways to handle the infinities: Schwinger, Feynmann, Tomonaga, and Stueckelberg. Thus QED was born, instead of a theory of the electron, it was a theory of the electromagnetic field, with electrons interacting in it. (Feynmann still worked with particles).

Scene shifts to the strong force. In 1956 Yang and Mills try to model the strong force with a nonabelian local gauge theory based on SU(2). Theory has problems. In about 1960 Gell-Mann and Ney'man separately develop the static SU(3) theory of the hadrons known at the time, the "eightfold way". Gell-Mann's names stick = quarks, up, down, and strange.

That's a static picture of particles, or maybe just symmetries, and Gell-Mann wouldn't commit to the particle picture. Physics goes into a detour, with the analytic S-matrix and nuclear democracy as described in the Dancing Wu-Li Masters. In the late 60's there are simultaneous breakthroughs:
1) Fadeev and Popov quantise Yang-Mills theory
2) Veltsman and t'Hooft renormalize Yang-Mills theory
3) The renormalization Group methodolgy is developed
4) Physicists at SLAC discover particles ("partons") inside the proton.
5) Weinberg and Salam develop the electroweak theory, the first successful local gauge theory, based on SU(2)xU(1). Glashow gets an assist for having the SU(2)xU(1) idea years before.

Now the development of QCD by Wilczek and others takes off and by the mid 70's the Standard Model has been constructed.

Meanwhile the physicists from the detour haven't completely given up the ideas they were working on. One of them was strings, and another was supersymmetry. Putting them together made a winner, superstrings.

Originally superstrings was not a field theory, but was like Dirac's a particle theory - except of course the particles were now strings.