Analysis: Why BICEP2 & PLAnck Are in Tension

[skydivephil]

An interesting blog post arguing the reason that BICEp 2 and PLAnck are in tension is becuase BICEP 2 underestimated galactic foreground emission.
http://resonaances.blogspot.co.uk/2014/05/is-bicep-wrong.html

 

[wolram]

http://physicsworld.com/cws/article/news/2014/mar/18/neil-turok-urges-caution-on-bicep2-results

Yesterday, researchers from the Background Imaging of Cosmic Extragalactic Polarization (BICEP2) telescope at the South Pole revealed that they have detected the first evidence for the primordial B-mode polarization of the cosmic microwave background (CMB). The astronomers claimed that the primordial B-mode polarization signal – which is related to primordial gravitational waves that flowed through the early universe – is the first direct evidence for cosmic inflation and has been measured to a statistical certainty of 3σ. Now, cosmologist and Perimeter Institute director Neil Turok, who worked on an inflationary model of his own with Stephen Hawking in the 1990s, urges caution and says that extensive experimental confirmation is necessary before BICEP2's results can be considered as evidence for inflation

It seems untimely to jump on the bicep2 bandwagon.

 

[phsopher]

Well, Turok doesn't really like inflation in the first place. He and Steinhardt have their cyclic models. So I would also take his skepticism with a pinch of the same. I'm not saying that we should just believe the BICEP result either, mind you. Still, it will be decided soon enough I think.

 

[wolram]

Well, Turok doesn't really like inflation in the first place. He and Steinhardt have their cyclic models. So I would also take his skepticism with a pinch of the same. I'm not saying that we should just believe the BICEP result either, mind you. Still, it will be decided soon enough I think.

I agree on both accounts, but here is an explanation from Not Even Wrong as to why we should be skeptical.

http://www.math.columbia.edu/~woit/wordpress/?p=6865

However, it seems they misinterpreted the Planck results: that map shows the polarization fraction for all foregrounds, not for the galactic dust only (see the “not CIB subtracted” caveat in the slide). Once you correct for that and rescale the Planck results appropriately, some experts claim that the polarized galactic dust emission can account for most of the BICEP signal...more.

 

[Dotini]

However, it seems they misinterpreted the Planck results: that map shows the polarization fraction for all foregrounds, not for the galactic dust only (see the “not CIB subtracted” caveat in the slide). Once you correct for that and rescale the Planck results appropriately, some experts claim that the polarized galactic dust emission can account for most of the BICEP signal...more.

ESA Planck researchers have explained polarized galactic dust emissions in a new NASA Sciencecast video:
http://m.space.com/26036-milky-way-s-magnetic-fingerprint-mapped-by-probe-video.html

http://www.allreadable.com/vid/scie...s-not-just-a-refrigerator-magnet-3554539.html <----readable format

http://www.iau.org/science/meetings/proposals/loi/2015/218/ <---related upcoming researches

 

[Chronos]

I view this as a competition and suspect both groups will end up feeling embarrassed.

 

[Dotini]

http://www.sciencedaily.com/releases/2014/06/140601150641.htm
http://www.newswise.com/articles/in...cates-amplification-of-cosmic-magnetic-fields

An article on new experimental research into the origin and amplification of cosmic magnetic fields.

 

[George Jones]

See also "Toward an Understanding of Foreground Emission in the BICEP2 Region" by Flauger, Hill, and Spergel,

http://arxiv.org/abs/1405.7351,

and cosmologist Peter Coles' blogs (newest at top, oldest at bottom) about this,

https://telescoper.wordpress.com/tag/bicep2/.

 

[Dotini]

Paul Steinhardt comments.

http://www.nature.com/news/big-bang-blunder-bursts-the-multiverse-bubble-1.15346

 

[bapowell]

Yeah, Steinhardt's take is odd. The question is whether inflation is falsifiable, not whether it is uniquely corroborate-able. B-modes simply cannot be used for falsification because they depend on the energy scale of inflation, which can be tuned to below detectable levels. So what? How does not detecting something a theory does not definitely predict weaken the case for this theory?

If not B-modes, how might we falsify inflation? I would think the lack of superhorizon polarization correlations in the CMB, or strongly non-adiabatic density perturbations would do it. Anybody have anything else?

To me, Steinhardt is arguing from his heart, not his head. He's long been an opponent of inflation and this articles smacks of this bias.

 

[Dotini]

See also "Toward an Understanding of Foreground Emission in the BICEP2 Region" by Flauger, Hill, and Spergel,

http://arxiv.org/abs/1405.7351,

See also "A joint analysis of Planck and BICEP2 B modes including dust polarization uncertainty",
Authors: Michael J. Mortonson, Uroš Seljak
http://arxiv.org/abs/1405.7351See also ‘No evidence for or against gravitational waves’
http://www.nature.com/news/no-evidence-for-or-against-gravitational-waves-1.15322

I had thought that the result was very secure,” Alan Guth, the cosmologist who first proposed the concept of cosmic inflation in 1980, and who is at the Massachusetts Institute of Technology in Cambridge, told Nature after learning about Flauger's talk. “Now the situation has changed.”

 

[Tanelorn]

If someone understands both sides of an argument without agreeing with either side are they an opponent? Neutral perhaps.

 

[bapowell]

If someone understands both sides of an argument without agreeing with either side are they an opponent? Neutral perhaps.

But he's securely on the other side, as a champion of ekpyrotic/cyclic models.

 

[Tanelorn]

ok thanks. Like the profile pic! Liked Bridges in K-Pax also, a truly wonderful movie.

 

[Dotini]

http://www.bbc.com/news/science-environment-27935479

On Thursday, the BICEP2 collaboration formally published its research in a peer reviewed journal - Physical Review Letters (PRL).

"I'm feeling like I'm at the eye of the storm”, said Prof Clem Pryke of the BICEP2 Collaboration.

In the paper, the US-led group stands by its work but accepts some big questions remain outstanding.

And addressing a public lecture in London, one of BICEP2's principal investigators acknowledged that circumstances had changed.

"Has my confidence gone down? Yes," Prof Clem Pryke, from the University of Minnesota, told his audience.

--------------------

'Data trumps models'

At his lecture at University College London, Prof Pryke explained his team's lowered confidence: "Real data from Planck are indicating that our dust models are underestimates. So the prior knowledge on the level of dust at these latitudes, in our field, has gone up; and so the confidence that there is a gravitational wave component has gone down. Quantifying that is a very hard thing to do. But data trumps models."

Prof Pryke spoke of the pressure he and his colleagues had been under since March. He said he never expected there would be such interest in their work, especially from mainstream media.

"I'm feeling like I'm at the eye of the storm," he told me.

"Look, the scientific debate has come down to this - we need more data. With the existing data that's out there, you can generate a lot of farce, a lot of blog posts, a lot of excitement and controversy, but you can't really answer the question scientifically. So, what you need is more data, and that's coming from Planck and it's coming from us."

Prof Marc Kamionkowski, from Johns Hopkins University, commented that what we were witnessing currently was "science in action".

 

[bcrowell]

BICEP2 result may have been wrong

http://www.washingtonpost.com/natio...0036ac-f7df-11e3-a606-946fd632f9f1_story.html

 

[marcus]

Here's the 20 June article in Nature:
http://www.nature.com/news/gravitational-wave-team-admits-findings-could-amount-to-dust-1.15440

It has a link to the recent publication by BICEP in Physical Review Letters (extensively modified from what they first announced) and probably as good a commentary as I've seen so far on this business.

 

[Dotini]

September 22, 2014 BBC article with news on the BICEP underestimated dust problem. Includes link to latest ESA paper.

http://www.bbc.com/news/science-environment-29305985#
One of the biggest scientific claims of the year has received another set-back.

In March, the US http://www.cfa.harvard.edu/CMB/bicep2/ said it had found a pattern on the sky left by the rapid expansion of space just fractions of a second after the Big Bang.

The astonishing assertion was countered quickly by others who thought the group may have underestimated the confounding effects of dust in our own galaxy.

That explanation has now been boosted by a new analysis from the European Space Agency's (Esa) Planck satellite.

In a paper published on the arXiv pre-print server, Planck's researchers find that the part of the sky being observed by the BICEP team contained significantly more dust than it had assumed.