Sunday, 10 October 2010

About Testing String Theory by Analogy

I like string theory, but as sad as it may seem we have to face that there is still no experimental test of it. And again, as desperate some people may be not to have wasted their lives (which actually is an unjustifiable fear), if string theory turns out to be not falsifiable, it is not science, but just a book keeping device. That's true. Without any falsifiable prediction, string theory becomes an extremely elegant and compact way to express our nature's knowledge up to date. If you are fine with that, no problem, but sincerely I prefer not to be sure that there will be no more experiments with explanations requiring new physics to be done even in principle. But I can be wrong.

But what this post is really about is alleged tests of string theory based on mathematical analogies. I can't deny that supersymmetry is a non-trivial prediction. If it is true, point to string theory. But other theories can be supersymmetric too. Another day, I heard about a paper using string theory to quantum computing, and these days I have heard a lot about holographic superconductors and AdS/CFT applied to condensed matter.

However, people must remember that applying the methods developed in one theory to other does not provide a proof of the former. The fact that you can use Feynman graphs in condensed matter and it works for explaining superconductivity does not mean that QFT is proved by it, experiments do. There is a difference between the mathematical methods developed to deal with a theory and the theory itself. Some people will say that there isn't, but that is dead wrong! The power of mathematics comes from abstraction and this allows for the use of the same tools to different problems. But physics is not only mathematics and depend on principles that are derived from and tested by experiments.

I am not saying that string theory is not science. On the contrary. It is a possible hypothesis which is being explored. However, it is not a proved theory no matter what the most intelligent people in the world say. Nature usually cares very little about what intelligent people think. There are many examples of it in human history. And the bottom line is that, even if the mathematics of string theory helps other theories, that does not count as a verification of string theory.

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