Following the recent rumor, some more useful information has been coming out about questions that some people are raising about whether the BICEP experiment really has seen signs of gravitational waves from inflation in the polarization of the cosmic microwave background radiation. The Washington Post has by far the best news article I’ve seen on the subject: it actually quotes people on the record, rather than repeating vague anonymous speculation.
The original rumor seems to be generally true, in the sense that it accurately described some criticisms that cosmologists were making about the BICEP analysis. The rumor does seem to have exaggerated and/or oversimplified things, and of course whether those criticisms are valid or not remains to be seen.
The best place I know of to get the technical details is this talk by Raphael Flauger. (Unfortunately, the video doesn’t show the slides as he’s talking, so if you want to follow it, download the slides first and try to follow along as he talks.) He argues that the dust models used by the BICEP team are inaccurate for a few reasons, mostly having to do with problems associated with the reason in the original rumor: the BICEP team appears to have used an image in a slide from a talk for part of their model, and they seem (he claims) to have misinterpreted what was in that slide. In addition (he claims), there are other errors associated with digitizing the image rather than using the real data (which BICEP doesn’t have access to). Flauger further claims that when you use a different (better?) dust model, the possible contribution of dust to what BICEP saw gets significantly larger, possibly large enough to explain their signal.
If BICEP has offered a detailed, technical rebuttal to this criticism, I haven’t seen it yet.
My personal assessment, based on obviously incomplete information: Flauger’s arguments seem to me to need serious consideration. BICEP needs to supply a detailed response. As of now, I don’t know whether he’s right or not, but my view has changed somewhat since the original rumor. The available information now does seem to me sufficient to substantially lower my own estimate of the probability that BICEP has seen primordial gravitational waves. I was fairly skeptical all along, but now I’m more skeptical. If you must know, I’d put the probability significantly below 50%.