This week’s issue of Nature has short articles by Atiyah and Witten, both addressing the issue of the current state of string theory.
Atiyah’s piece is an interesting review of Lawrence Krauss’s new book Hiding in the Mirror entitled Pulling the strings, and it concentrates on what Krauss has to say about the relation of mathematics and physics. Krauss ends his book quoting the mathematician Hermann Weyl as choosing beauty over truth, remarking that physicists don’t have this luxury. Atiyah points out the story of Weyl’s work on gauge theory, which Weyl published over Einstein’s strong argument that it was physically wrong. The idea was just so beautiful that Weyl felt there had to be something to it, an opinion that turned out to be amply justified as the concept of a gauge theory has turned out to be among the most fundamental ideas in theoretical physics.
Witten’s piece is entitled Unravelling string theory and it tells the story of how he got interested in string theory and offers a defense of its continued study despite the lack of progress during the past 21 years in using it to come up with a unified theory. His defense consists of three points:
1. It appears to be a consistent generalization of QFT, and is worth study on that grounds alone.
2. It incorporates general relativity and provides a “rough draft” of particle physics.
3. Research on string theory has led to all sorts of spin-offs: insights into confinement, black-holes, mathematics.
Those are certainly the strongest arguments for working on string theory, but I find it disappointing that Witten chooses to ignore much of what has been happening in string theory over the last few years. He addresses only by indirect allusion the whole issue of the landscape and the strong possibility that the string theory framework for unification is inherently incapable of predicting anything. Witten would do particle theory a huge favor by at least acknowledging that if the string theory landscape really exists, it is not, as many seem to think, a new paradigm for how to pursue theoretical physics, but instead the end of hopes for this idea about how to achieve unification.