The BICEP2 paper is now out in Physical Review Letters, with major revisions to its conclusions from the preprint/press conference version of last March. For another sort of associated revision, compare this (from a March 17 Stanford press release):
Linde, now a professor of physics at Stanford, could not hide his excitement about the news. “These results are a smoking gun for inflation, because alternative theories do not predict such a signal,” he said. “This is something I have been hoping to see for 30 years.”
to this (from an interview with Linde in the latest New Scientist):
I don’t like the way gravitational waves are being treated as a smoking gun.
If we found no gravitational waves, it wouldn’t mean inflation is wrong. In many versions of the theory, the amplitude of the gravitational waves is miserably small, so they would not be detectable.
Last month, Resonaances broke the news that there was a problem with the BICEP2 claims, specifically with the bottom line (and punch line) of their preprint abstract:
Subtracting the best available estimate for foreground dust modifies the likelihood slightly so that r=0 is disfavored at 5.9σ.
Back then the BICEP official reaction to the Resonaances claim that they were admitting to a mistake was “We’ve done no such thing.” Post-refereeing, there have been extensive changes in the paper (for example, the “DDM2” dust model based on scraped Planck data is gone), and the bottom line of the abstract has been changed to:
Accounting for the contribution of foreground, dust will shift this value [non-zero r at 7.0 sigma] downward by an amount which will be better constrained with upcoming data sets.
If the BICEP collaboration is still not admitting a mistake in their treatment of Planck data or the bottom line of their preprint, then it seems that referees have told them they can’t publish these in PRL.
Back in March the BICEP2 results made the front page of the New York Times with a Dennis Overbye story Space Ripples Reveal Big Bang’s Smoking Gun, but today the NYT has Astronomers Hedge on Big Bang Detection Claim, which explains well what has been going on.
Using for the first time the newest Planck maps available, Puget and his collaborators have directly examined the polarization of dust in these high galactic regions rather than extrapolating from dustier regions in the plane of the Milky Way. Averaging over some 350 high-galactic-latitude patches of sky similar in size to the region observed by BICEP2, Puget reported that polarization from interstellar dust grains plays a significant role and might account for much of the BICEP2 signal that had been attributed to inflation-generated gravitational waves. Puget told Nature that an article detailing these findings would be published in about six weeks.
Update: I’ve been watching Paul Steinhardt’s talk at Strings 2014, where he’s giving a dramatic attack on the way inflationary cosmology is being pursued as in violation of the scientific method. One thing he does is put up exactly the Linde quotes from this posting.