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Can anybody elaborate on the implications of the BICEP2 result for string theory?

The discussion here What experiment would disprove string theory? suggests that refuting string theory is rather difficult. It did not mention that planned/ongoing experiments in the near future could exclude many string models by measuring the polarization of the CMB.

I now read that the BICEP2 result might rule out lots of string theory models. Is that true? If so, why? Is this result in the so-called "swampland"? How big a blow is this for string theory?

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innisfree
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  • anecdata: The string theorists I know are delighted about this result. – user1504 Mar 18 '14 at 11:07
  • My anecdata: alternatives to string theory theorists are happy. Is each side claiming a victory?! – innisfree Mar 18 '14 at 11:41
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    I think this post is the best place to start: http://motls.blogspot.com/2014/03/bicep2-primordial-gravitational-waves.html The result helps to rule out a large number of models. The gravity waves weren't predictions of string theory, however, it was a prediction of applying quantum field theory to gravity. We should find that confusing. It came from a quantum gravity theory, but an incomplete application of it. It looks like, however, string theory would directly predict the r value itself. So maybe that's where we need those theories. – Alan Rominger Mar 18 '14 at 12:23
  • Note to posterity: the claimed discovery of primordial gravitational waves that this question references is now agreed to have been in error. See for example "Gravitational waves discovery now officially dead". – Sten Mar 30 '23 at 12:47

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