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The BICEP2 results, unless I am mistaken, are a measurement of CMB polarization, i.e. photon polarization. That is, taken at face value they say nothing about gravity directly. Now, we can start to make some assumptions in order to see what this result tells us about other physics like gravity. These assumptions fall into 2 very different categories: (i) very general statements about the nature of quantum mechanics, field theory, and quantum field theory and (ii) specific field-theoretic model dependent assumptions. Assuming this is true,

(1) What does the BICEP2 results say about gravitational waves? And what assumptions did we need to make in order to make this statement(s) (general or model dependent assumptions)?

(2) What do the BICEP2 results tell us about quantum gravity? And what assumptions did we need to make in order to make this statement(s) (general or model dependent assumptions)?

(3) Lastly, are my questions (1) and (2) actually the same question?

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  • $\begingroup$ This blog post by Matt Strassler is worth checking out profmattstrassler.com/2014/03/18/… $\endgroup$ – sunspots Mar 19 '14 at 14:13
  • $\begingroup$ @sunspots - thanks for the link. I read all the blogs already, but I am looking for a something more technical than Strassler's explanation. $\endgroup$ – DJBunk Mar 19 '14 at 14:17
  • $\begingroup$ 1.I don't see BICEP2 as providing any new information about gravitational waves themselves. I think the general relativity prediction of gravitational waves was already well-accepted. Maybe you could think of BICEP2 as another confirmation of this accepted theory. 2. This paper is a more-techincal discussion of quantum gravity in relation to the CMB: arxiv.org/pdf/1309.5343v2.pdf $\endgroup$ – DavePhD Mar 19 '14 at 15:58
  • $\begingroup$ @DJBunk here's a back of the envelope by Preskill concerning BICEP2 and Inflation: quantumfrontiers.com/2014/03/23/… $\endgroup$ – sunspots Mar 24 '14 at 2:34
  • $\begingroup$ @DJBunk this paper is written prior to BICEP2 results, but covers Inflation in sufficient depth: arxiv.org/pdf/0907.5424v2.pdf $\endgroup$ – sunspots Mar 24 '14 at 23:45

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