Comment on How about testing our ideas?

Mon, 17 Sep 2012 07:57:16 GMT

The trouble with string theory as a theory of spacetime is that it takes place in a fixed space time background

That's just an approximation. Those situations (flat space, hyperbolic space) are really just asymptotically fixed - the form of the space-time in the infinite past or the infinite future is fixed. But in between, you can have topology change.

String theory in positively curved space may even allow for topologically distinct asymptotic outcomes, but that is still a topic of great confusion.

There is a standard paradigm for applying string theory to the real world - grand unification, broken supersymmetry, compactification. I'd give that about a 50% chance of being correct. Then there are increasingly unfamiliar scenarios, the extreme of which would be a theory in which you don't even have strings or branes, but in which some of the abstract properties of string theory (e.g. the algebraic structure of the amplitudes) still hold. The twistors could swing either way here: twistorial variables may exist for an orthodox string scenario, but there may also be twistorial theories way outside the usual M-theoretic synthesis.

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