Monday, March 17, 2014

[1403.3985] BICEP2 I: Detection Of B-mode Polarization at Degree Angular Scales

[1403.3985] BICEP2 I: Detection Of B-mode Polarization at Degree Angular Scales:



We report results from the BICEP2 experiment, a Cosmic Microwave Background (CMB) polarimeter specifically designed to search for the signal of inflationary gravitational waves in the B-mode power spectrum around l=80. The telescope comprised a 26 cm aperture all-cold refracting optical system equipped with a focal plane of 512 antenna coupled transition edge sensor (TES) 150 GHz bolometers each with temperature sensitivity of approx. 300 uk.sqrt(s). BICEP2 observed from the South Pole for three seasons from 2010 to 2012. A low-foreground region of sky with an effective area of 380 square degrees was observed to a depth of 87 nK-degrees in Stokes Q and U. In this paper we describe the observations, data reduction, maps, simulations and results. We find an excess of B-mode power over the base lensed-LCDM expectation in the range 30<l<150, inconsistent with the null hypothesis at a significance of $>5\sigma$. Through jackknife tests and simulations based on detailed calibration measurements we show that systematic contamination is much smaller than the observed excess. We also estimate potential foreground signals and find that available models predict these to be considerably smaller than the observed signal. These foreground models possess no significant cross-correlation with our maps. Additionally, cross-correlating BICEP2 against 100 GHz maps from the BICEP1 experiment, the excess signal is confirmed with $3\sigma$ significance and its spectral index is found to be consistent with that of the CMB, disfavoring synchrotron or dust at $2.3\sigma$ and $2.2\sigma$, respectively. The observed B-mode power spectrum is well-fit by a lensed-LCDM + tensor theoretical model with tensor/scalar ratio $r=0.20^{+0.07}_{-0.05}$, with r=0 disfavored at $7.0\sigma$. Subtracting the best available estimate for foreground dust modifies the likelihood slightly so that r=0 is disfavored at $5.9\sigma$.



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3 comments:

Bert Morrien said...

This seems to be the very first detection of gravitational waves. Lawrence Krauss sees this as evidence for quantum gravity, hence this could also be the very first indirect observation of gravitons.
If this is true, Erik Verlinde might be in trouble, because he is developing a theory in which gravitation is an emerging force due to entropy / information, so I am quite curious about his view on the new findings.

Eduardo Cantoral said...

Mr. Morrien, I am more interested in Inflation theories which finally will be rejected, and Physics will be an experimental science again, as it must.

Bert Morrien said...

Dear Eduardo Cantoral,

So far inflation is a conjecture that could well become an established theory if the results of this experiment can be repeated. I think this is a splendid example of experimental science.
Theoretical physics done by people like Erik Verline and Lawrence Krauss is important, because it offers the possibility to find new directions in unknown territory. Lamenting that this might be speculative territory without trying to explore it is a sure way to miss it completely, also when it is something real.

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