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    • CommentRowNumber1.
    • CommentAuthorUrs
    • CommentTimeMar 24th 2014
    • (edited Mar 24th 2014)

    Created BICEP2, currently with the following text:


    BICEP2 is the name of an astrophysical experiment which released its data in March 2014. The experiment claims to have detected a pattern called the “B-mode” in the polarization of the cosmic microwave background (CMB).

    This data, if confirmed, is widely thought to be due to a gravitational wave mode created during the period of cosmic inflation by a quantum fluctuation in the field of gravity which then at the era of decoupling left the characteristic B-mode imprint on the CMB. This fact alone is regarded as further strong evidence for the already excellent experimental evidence for cosmic inflation as such (competing models did not predict such gravitational waves to be strong enough to be detectable in this way).

    What singles out the BICEP2 result over previous confirmations of cosmic inflation is that the data also gives a quantitative value for the energy scale at which cosmic inflation happened (the mass of the hypothetical inflaton), namely at around 10 1610^{16}GeV. This is ntoeworthy as being only two order of magnituded below the Planck scale, and hence 12 or so orders of magnitude above energies available in current accelerator experiments (the LHC). Also, it is at least a curious coincidence that this is precisely the hypothetical GUT scale.

    It is thought that this value rules out a large number of variant models of cosmic inflation and favors the model known as chaotic inflation.

    • CommentRowNumber2.
    • CommentAuthorzskoda
    • CommentTimeMar 24th 2014

    I am a bit disappointed that my astrophysics colleagues from Wisconsin are not the part of this amazing collaboration, as they contributed (and were part of the crew there) to some earlier South Pole astrophysical projects, most remarkably AMANDA (neutrino probes deeply in the ice).

    • CommentRowNumber3.
    • CommentAuthorUrs
    • CommentTimeMar 24th 2014

    My understanding is that quite a few people were disappointed that they didn’t make to be associated with this event. In particular the people in the much larger scale Planck experiment are seeing their Nobel prize disappear right in front of them. Unless of course the BICEP2 results will end up not being confirmed…

    • CommentRowNumber4.
    • CommentAuthorTodd_Trimble
    • CommentTimeMar 24th 2014

    Maybe I was skimming too quickly and didn’t see it, but what does BICEP stand for?

    • CommentRowNumber5.
    • CommentAuthorzskoda
    • CommentTimeMar 24th 2014
    • (edited Mar 24th 2014)

    Is the scale of intensity of these gravitational wave modes previously predicted ? How many orders of magnitude was the theoretical uncertainty (before the measurement) ?

    • CommentRowNumber6.
    • CommentAuthorUrs
    • CommentTimeMar 24th 2014

    @Todd, right, I have added that now, it’s for Background Imaging of Cosmic Extragalactic Polarization.

    @Zoran, so all I know is that people say this is very well in agreement with what is predicted by Andrei Linde’s chaotic inflation. For error discussion and the like I can only refer you to the various expert discussion on the web, such as maybe also this one here.

    The general consensus seems to be that the measurement and error discussion is carefully done, but that there remain some disconcerting incompatibilities with previous Planck measurement. Some experts apparently said that these are serious, while others said they are not, I don’t know. Some said the good news is that Planck will have much more data on this just a little bit later this year, while others I heard saying (forget where) that precisely that B-mode signal claimed now will be hard for Planck to say much about.

    So: stay tuned.

    • CommentRowNumber7.
    • CommentAuthorUrs
    • CommentTimeMar 24th 2014
    • (edited Mar 24th 2014)

    @Zoran,

    you can tell how sure they feel that this confirms the predictions of Linde’s “chaotic inflation” from the picture here (scroll down a bit) :-)

    • CommentRowNumber8.
    • CommentAuthorzskoda
    • CommentTimeMar 24th 2014

    bicep :)

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