Pulsar wrote:I'm sure that many still have questions. Well, good news! Finally, here's a paper that explains everything!

The CMB flexes its BICEPs while walking the Planck (Scott & Frolop, 2014)

kennyc wrote:Love the Title!

BICEP2 has achieved the deepest observations yet of CMB polarization. These measurements have revealed a particular signature in the polarization that is quite hard to explain – sometimes called ‘B-modes’, but more technically known as ‘a swirly pattern’. These results are certainly exciting [3], since they have implications for a parameter called r. On learning about these new results, the main question that people have is ‘what is r?’ The answer is that r equals 0.2 from BICEP2.

[3] So exciting in fact, that one of us (A.F.) came out of retirement especially to write this paper.

It is fairly well established that the Universe contains lumps [4]. These lumps can either be in a form that come in a wide range of scales (called ‘scalars’) and those which help resolve tensions in the data (called ‘tensors’).

[4] Some of our best friends are lumps.

We can imagine that our CMB sky is effectively the same as the surface of a star like the Sun in some other dimension. In other words we have a relationship between Another-dimension’s Sun and the CMB, which we could call the AdS-CMB correspondence.

The conformal invariance of the Weyl projection operators across the boundary mean that tachyonic fields suffer a conjugation, leading to a reciprocal Lyapunov entropy [14].

[14] Or something like that.

All of this makes complete sense if we simply consider the entire Universe to be turned inside-out, as well as
inverted in scale and time. The only alternative being discussed in the literature would be to suppose that experimental results might shift slightly, so that the Planck, BICEP2 and other cosmological data-sets become consistent with the so-called V / m2φ2 inflationary potential. However, that would imply that the effective potential in the early Universe had a minimum with a quadratic shape. Such a shape would be unprecedented in physics, and hence that solution seems quite preposterous compared with ours

hackenslash wrote:It's the last remaining untested prediction of General Relativity, and it has some interesting consequences. Firstly, it can provide a window past our current observational limit of 380,000 years after the onset of expansion, because the universe was opaque to photons until that time. A workable gravitational wave observatory could potentially allow observation all the way back to the Planck time.

Also, dependent on the specific nature of the gravitational waves, some cosmologies can be falsified, such as the 'brane-worlds' model of Turok and Steinhardt.

Is BICEP wrong?

Barring a loose cable, the biggest worry about the BICEP signal is that the collaboration may have underestimated the galactic foreground emission. BICEP2 performed the observations at only one frequency of 150 GHz which is very well suited to study the CMB, but less so for polarized dust or synchrotron emission. As for the latter, more can be learned by going to higher frequencies, while combining maps at different frequencies allows one to separate the galactic and the CMB component. Although the patch of the sky studied by BICEP is well away from the galactic plane, the recently published 353 GHz polarized map from Planck demonstrates that there may be significant emission from these parts of the sky (in that paper the BICEP patch is conveniently masked, so one cannot draw any quantitative conclusions). Once the dust from the BICEP announcement had settled, all eyes were thus on precision measurements of the galactic foreground. The rumors that have been arriving from the Planck camp were not encouraging, as they were not able to confirm the primordial B-mode signal. It seems that experts now put a finger on what exactly went wrong in BICEP.

(continues)

newolder wrote:Planck intermediate results. XXIX. All-sky dust modelling with Planck, IRAS, and WISE observations
Some of the eagerly awaited Planck results that will get the juices flowing soon, i guess.

Rumraket wrote:

newolder wrote:Planck intermediate results. XXIX. All-sky dust modelling with Planck, IRAS, and WISE observations
Some of the eagerly awaited Planck results that will get the juices flowing soon, i guess.

Who can read and understand this? Some body give us the layman's version.

Calilasseia wrote:

Rumraket wrote:

newolder wrote:Planck intermediate results. XXIX. All-sky dust modelling with Planck, IRAS, and WISE observations
Some of the eagerly awaited Planck results that will get the juices flowing soon, i guess.

Who can read and understand this? Some body give us the layman's version.

Right, here's what the paper sets out to do.

There exists a model, which describes how dust in interstellar space behaves, wwhich incorporates the following features:

[1] Optical extinction (AV): in short, how much it absorbs light reaching us from distant objects;

[2] Starlight intensity heating (Umin): in short, how its temperature changes, as it absorbs light from stars, as a function of the intensity of the light, and the distance from the dust of the stars generating that light. Here, 'light' encompasses both visual and IR/UV parts of the spectrum, whereas in [1], the specification of optical extinction restricts the use of 'light' therein to cover the visual spectrum only.

Comparing the data generated by the model, with the data now present in quantity from various star and deep sky surveys, the authors found that whilst the model works in some instances, there are significant discrepancies in others. As a corollary, parts of the model need to be revised. In particular, the authors found that AV depends upon Umin in ways that were not previously predicted, and adopting the new relationship for AV in terms of Umin rectifies the discrepancies.

However, introducing this rectification means that certain physical assumptions present in the dust model need to be revised. Until that revision is complete, and a new, better dust model is in place, the current dust model cannot be relied upon as a means of validating results dependent upon that dust model. Which includes the B-mode work.

B.B.C. Article
One of the biggest scientific claims of the year has received another set-back.
In March, the US BICEP team 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.
This new information does not mean the original claim is now dead. Not immediately, anyway.

(Continues)

Cosmic inflation: BICEP 'underestimated' dust problem

BICEP's South Pole telescope targeted what the team hoped was a relatively clean part of the sky

In March, the US BICEP team 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.

This new information does not mean the original claim is now dead. Not immediately, anyway.

Cosmic 'ripples'
The BICEP and Planck groups are currently working on a joint assessment of the implications, and this will probably be released towards the end of the year.

However, if the contention is eventually shown to be unsupportable with the available data, it will prove to be a major disappointment, especially after all the initial excitement and talk of Nobel Prizes.

What BICEP (also known as BICEP2) claimed to have done was find the long-sought evidence for "cosmic inflation".

This is the idea that the Universe experienced an exponential growth spurt in its first trillionth of a trillionth of a trillionth of a second.

The theory was developed to help explain why deep space looks the same on all sides of the sky - the notion being that a very rapid expansion in the earliest moments could have smoothed out any unevenness.
......

• BICEP Instrument: Right. Whatever happened one should not forget that, at the instrumental level, BICEP was a huge success.
  
• ArXiv first: Right. The BICEP paper has undergone a thorough peer-review process of the best possible kind that included the whole community.
  
• Press conference: Right. Given the importance of the discovery and how news spread over the blogosphere, the net effect on the public would be exactly the same if they just submitted to ArXiv.
  
• Data scraping: Right. You should always use all publicly available relevant information; it's as simple as that.
  
• Inflation spin: Wrong. Now that the result does not stand, the inflation picture and, by association, the whole big bang scenario is undermined in public perception.
  
• Quality control: Wrong. From what I heard, the unfortunate analysis of the dust polarization fraction based on the Planck polarization data was performed by a single collaboration member and never cross-checked.
  
• Denial: Wrong. The error in the estimate of the dust polarization fraction was understood soon after the initial announcement, and BICEP leaders were aware of it. Instead of biting the bullet, they chose a we-stand-by-our-results story.

Despite earlier reports of a possible detection, a joint analysis of data from ESA’s Planck satellite and the ground-based BICEP2 and Keck Array experiments has found no conclusive evidence of primordial gravitational waves.