A major discovery, BICEP2 and B-modes The cosmology rumour mill exploded today. Harvard Astrophysics have issued a press release stating that, on Monday, they will announce a major discovery. This is the only hard-evidence of anything interesting on the way and it could be an announcement of anything that fits under the label of astrophysics. This is important to keep in mind. However, for one reason or another (that is hard to nail down), cosmologists are suggesting that it is going to be about cosmology. The speculation is that it will be about the BICEP2 experiment, which has been measuring the polarisation in the CMB. The speculation is that BICEP2 have seen primordial B-mode polarisation. If this speculation is true, this would be a result immense in its significance. Primordial B-modes would be a smoking gun signal of primordial gravitational waves. This, alone, makes such a discovery important. Gravitational waves have not yet been observed, but are a prediction from general relativity. Therefore, such a discovery would be on the same level of significance as the discovery of the Higgs particle. We were almost certain it would be there, but it is good to finally see it. However, the potential significance of such a result goes further because these primordial gravitational waves would need a source. The theory of cosmological inflation would/could be such a source. Inflation is a compelling theory, not without some problems, for how the universe evolved in its very earliest stages. If it occurred when the universe had a large enough temperature, it would generate primordial gravitational waves large enough to tickle the CMB enough to make these B-modes visible in the polarisation. As of yet, inflation has passed quite a few observational tests, but nothing has been seen that could be described as smoking gun evidence. A spectrum of primordial gravitational waves would very nearly be such a smoking gun. If the spectrum was scale invariant (i.e. if the gravitational waves have the same amplitude on all distance scales) that would be a smoking gun for inflation and accolades, Nobel Prizes, etc, etc, would flow accordingly. All of this is just speculation, but some of it does seem to be coming from reputable sources. And some of my colleagues have been talking about tip-offs from people who wish to remain anonymous, so I figured Id collect all the speculation I know of here in a post (let me know if Ive missed anything): Richard Easther, on the rumour and its implications: excursionset/blog/2014/3/15/the-smoking-gnu Bruce Bassett, on the probability that the rumours are true: cosmobruce.wordpress/2014/03/14/108/ The Guardian (the first major news source to pick up on this) with comments from various prominent cosmologists: theguardian/science/2014/mar/14/gravitational-waves-big-bang-universe-bicep?CMP=twt_gu The PI of BICEP2, John Kovac, gave a talk at the annual COSMO conference last year that had some pretty ambitious claims for how sensitive BICEP2 and similar experiments were going to be, so... well... well know on Monday. It should also be noted that, although the existence of these gravitational waves is a prediction of inflation, their amplitude is a free parameter and an amplitude this big is potentially a little surprising (for me, lower temperature inflation models just seem more compelling, others might disagree).
Posted on: Tue, 18 Mar 2014 12:59:52 +0000
Trending Topics
Recently Viewed Topics
© 2015