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Previous Next Up Topic Cosmology / Alternative Cosmology / Proof of inflation? (6402 hits)
By Ritchie Annand Date 2014-03-18 17:30
This has been bumping around the blogosphere:

The article said:

The Background Imaging of Cosmic Extragalactic Polarization 2 (BICEP2) experiment at the South Pole found a pattern called primordial B-mode polarization in the light left over from just after the big bang, known as the cosmic microwave background (CMB). This pattern, basically a curling in the polarization, or orientation, of the light, can be created only by gravitational waves produced by inflation. “It looks like a swirly pattern on the sky,” says Chao-Lin Kuo, a physicist at Stanford University, who designed the BICEP2 detector. “We’ve found the smoking gun evidence for inflation and we’ve also produced the first image of gravitational waves across the sky.”


I can't help the feeling that they're reading into it, not necessarily on the side of what they see but what it means, largely due to the "inglorious hack" nature of inflationary theory and a putative nearer origin of the microwave background.

Thoughts?
By Mike Petersen Date 2014-03-18 22:19
My immediate thoughts are clouded by the references to someone (forgot who) notifying Andre Linde of the results at his home...it was almost like a Publisher's Clearing House ad for the next winner.  Anyway, my first thought was...."What happened to notifying Guth?"
By Mike Petersen Date 2014-03-21 09:04
Here is what Neil Turok has to say about it at physicsworld.com:

Neil Turok urges caution on BICEP2 results
By Ritchie Annand Date 2014-03-23 05:29
The article said:

Indeed, the tensor-to-scalar ratio of 0.20 that BICEP2 measured is considered to be significantly larger than that expected from previous analyses of data. But the BICEP2 researchers said in their press conference yesterday that they believe certain tweaks could be made to an extension of the ΛCDM cosmological model that could make the two results agree.

"But these tweaks would be tremendously ugly....and in fact, I believe that if both Planck and the new results agree, then together they would give substantial evidence against inflation!" exclaims Turok, further explaining that "[we] must be careful before we treat them as true".


Most folks seem to be interpreting the ratio as meaning that inflation just started earlier. I think some are hoping that the ratio turns out to be lower.

The comments on that thread are great fun.

Someone referenced Brandenberger's 2011 paper, Is the Spectrum of Gravitational Waves the “Holy Grail” of Inflation?. That paper has some fun bits to it, such as:

Brandenberger said:

It is important to realize that a scale-invariant spectrum of adiabatic fluctuations as the origin of structure in the universe was already postulated a declare before the development of inflationary cosmology [7], and that ANY scenario which produces an almost scale-invariant spectrum of adiabatic fluctuations agrees equally well with the observations. This point is generally recognized, but it is then often claimed that since inflation produces a nearly scale-invariant spectrum of gravitational waves, the discovery of such a spectrum will confirm inflation. However, as will be emphasized here, this logic is incorrect.


There's also @telescoper's interesting blog posting, "BICEP2: Is the Signal Cosmological?":

@telescoper said:

Taking all this together I have to say that I stick to the point of view I took when I first saw the results. They are very  interesting, but it is far too earlier to even claim that they are cosmological, let alone to start talking about providing evidence for or against particular models of the early Universe. No doubt I’ll be criticized for trying to put a wet blanket over the whole affair, but this is a measurement of such potential importance that I think we have to set the bar very high indeed when it comes to evidence. If I were running a book on this, I would put it at no better than even money that this is a cosmological signal.


Still, everything we find helps narrow down what's actually in our universe.
By Ritchie Annand Date 2014-06-10 04:33
It looks as though erring on the side of caution might have turned out to be correct:

The article said:

The BICEP2 instrument detects radiation at only one frequency, so cannot distinguish the cosmic contribution from other sources. To do so, the BICEP2 team used measurements of galactic dust collected by the Wilkinson Microwave Anisotropy Probe and Planck satellites, each of which operates over a range of other frequencies. When the BICEP2 team did its analysis, the Planck dust map had not yet been published, so the team extracted data from a preliminary map that had been presented several months earlier. Now a careful reanalysis by scientists at Princeton University and the Institute for Advanced Study, also in Princeton, has concluded that the BICEP2 B-mode pattern could be the result mostly or entirely of foreground effects without any contribution from gravitational waves. Other dust models considered by the BICEP2 team do not change this negative conclusion, the Princetonteam showed (R. Flauger, J. C. Hill and D. N. Spergel, preprint at http://arxiv.org/abs/1405.7351; 2014).


I'd call that more a limitation than a "blunder", but it still may mean back to the drawing board (or continue from the drawing board as is happening with other experiments) for gravity waves.

I'm a bit ambivalent about gravity waves. What will it mean if we don't find them?
By Mike Petersen Date 2014-06-20 12:26
oooops
By Ritchie Annand Date 2014-06-27 05:47
What the heck are people talking about in there for 5700+ comments?

The article said:

"We know that galactic dust emits polarized radiations. We see that in many areas of the sky, and what we pointed out in our paper is that pattern they have seen is just as consistent with the galactic dust radiations as with gravitational waves," Spergel told AFP last week.


...

The article continues said:

"I think in retrospect, they should have been more careful about making a big announcement," he said.


:)
By Mike Petersen Date 2014-06-27 09:23 Edited 2014-06-27 10:51
And now this:  Has the Cosmology Standard Model become a Rube Goldberg Device?

I'm actually not surprised that astronomical science is finally coming to grips with the Cosmological SM.  The recent spate of numerical data has finally put to the test a lot of what went into it.  It would have been unthinkable even five years ago for Universe Today to publish such an article. 

Yes, I believe "Rube Goldberg Device" is a perfect way to describe the SM.  The article pointed out a good parallel to this with the situation that existed until Einstein had his "miracle year" of 1905 and his General Theory of Relativity established in the years 1907 to 1922 (when it was finally shown during a total eclipse that light was indeed bent in gravitational fields.)  We need another Einstein to fix what's wrong with Cosmology!

Is there one out there?
By Ritchie Annand Date 2014-06-28 06:53
Why oh why did they misspell two important names in that article. Roger Penrose, not Primrose, and Brian Greene with a final e.

Damn you, Universe Today Autocorrect? :)

I was a little unclear what linkages were being made between the Standard Model (particle physics) and the "Standard" model (Big Bang Theory) - perhaps I've been missing reading the Higgs -> Inflation pro (and now apparently con) papers.

That said, it's been a Rube Goldberg device for a while, you're right; been quite tough to get predictions out of that thing that pan out :)
By Ritchie Annand Date 2015-02-02 08:21
And Slate half a year later:

Slate said:

The bottom line is that they do still see some evidence for gravitational waves affecting the light from the early Universe, but it doesn’t look like it rises to being statistically significant, and it’s certainly not as strong as they first thought.
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