Bewijs voor inflatie gevonden?

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Op maandag 17 maart 2014 15:12 schreef RobbieRonald het volgende:
Eigenlijk kunnen we dus steeds meer stellen dat de oerknal een feit is. Tenzij het een ander proces was dat zéér veel overeenkomt met een oerknal.

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Our universe burst into existence in an event known as the Big Bang 13.8 billion years ago. Moments later, space itself ripped apart, expanding exponentially in an episode known as inflation. Telltale signs of this early chapter in our universe's history are imprinted in the skies, in a relic glow called the cosmic microwave background. Recently, this basic theory of the universe was again confirmed by the Planck satellite, a European Space Agency mission for which NASA provided detector and cooler technology.

But researchers had long sought more direct evidence for inflation in the form of gravitational waves, which squeeze and stretch space.

"Small, quantum fluctuations were amplified to enormous sizes by the inflationary expansion of the universe. We know this produces another type of waves called density waves, but we wanted to test if gravitational waves are also produced," said project co-leader Jamie Bock of NASA's Jet Propulsion Laboratory, Pasadena, Calif., which developed the BICEP2 detector technology. Bock has a joint appointment with the California Institute of Technology, also in Pasadena.

The gravitational waves produced a characteristic swirly pattern in polarized light, called "B-mode" polarization. Light can become polarized by scattering off surfaces, such as a car or pond. Polarized sunglasses reject polarized light to reduce glare. In the case of the cosmic microwave background, light scattered off particles called electrons to become slightly polarized.

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What are we seeing in BICEP2's snapshots of the CMB polarization?
The most important result were focused on is the implications of the signal we detected for models of inflation. We are seeing a direct image of a [primordial] gravitational wave, causing light to be polarized in a particular way. The CMB is a snapshot of the Universe 380,000 years after the Big Bang, when the radiation first streamed freely into space, but the gravitational-wave signal was imprinted on the CMB a tiny fraction of a second after the birth of the Universe.

What else is important about the finding?
Everyone in cosmology knows but it is not widely appreciated that the prediction about B modes from inflation relies not just on the phenomenon of gravitational waves but on the quantization of gravity itself. Inflation assumes that everything started out as quantum fluctuations that then got amplified by inflation. So at a very deep level, this finding relies on the connection between quantum mechanics and gravity being right.

Did it cause concern that BICEP2 had detected a B-mode polarization signal that was nearly twice as high as data from the Planck spacecraft suggested?
The Planck data [released so far] came from a temperature map of the CMB, not from a direct polarization measurement. We were always committed to doing an extra careful job on this analysis, but I will admit that the presence of a larger signal-to-noise ratio in our data [compared with the Planck data] sharpened our focus in thinking about every possible systematic explanation over the past three years that could have falsified the signal. Weve done the most extensive systematic analysis that Ive ever been involved in by far.

When did you first realize that you had detected the long-sought 'smoking gun for inflation'?
Last fall, when we first compared the BICEP2 signal with BICEP1. That was very powerful because BICEP1 had very different detectors and used much older technology. So the fact that we were able to see the same signal with this completely different kind of telescope laid a lot of lingering doubts to rest. The remaining sceptics on our team were convinced at that point.

In early December I was at the South Pole and we had a very intense meeting where I laid out all the tests the data had passed and the milestones still to be achieved, and that we would publish if those remaining tests were passed.

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About the detection
Have you detected B-modes from inflation?
We have detected B-mode polarization at precisely the angular scales where the inflationary signal is expected to peak with very high significance (> 5 sigma). We have extensively studied possible contamination from instrumental effects and feel confident we can limit them to much smaller than the observed signal. Inflationary gravitational waves appear to be by far the most likely explanation for the signal we see.

Couldnt it just be galactic emission or polarized dust?
The data disfavor this. The best current models of polarized galactic emission in our observing region show it to be much fainter than the signal we see. Also, there is little evidence for correlation between our B-mode maps and the predicted pattern from the galaxy. Finally, within our own data, the color of the B-modes found by comparing different frequencies is consistent with CMB but disfavors galactic contamination.

Have you detected a gravitational wave?
The frequency of the cosmic gravitational waves is very low, so we are not able to follow the temporal modulation. However, we are indeed directly observing a snapshot of gravitational waves through their imprints on matter and radiation over space. Ordinary density perturbations cannot create the pattern we observe. The presence of a water wave can be detected by feeling its up-and-down motion or by taking a picture of it. We are doing the latter.

About the science
What is B-mode polarization and how is it generated by inflation?
Measuring the polarization of the Cosmic Microwave Background at different points on the sky determines a direction and polarized intensity (the polarized intensity of the CMB is less than 1/1,000,000 its total brightness). This can be visualized as a map of little line segments at every spot on the sky, the patterns of which we analyze. B-mode polarization is essentially the swirly part of that pattern (known mathematically as the curl). For the density fluctuations that generate most of the polarization of the CMB this part of the primordial pattern is exactly zero.
[This is because density flows in the early universe go into or out of dense regions, and the polarization lines up with these flows in a way that doesn't swirl, producing only so-called E-mode polarization. To generate a B-mode pattern in the early universe you need gravitational waves.]
Inflation magnifies quantum fluctuations, which exist even in vacuum. The quantum fluctuations in the inflation field itself (inflaton) become the density fluctuations seen in the CMB and at much later times in galaxy distributions. During inflation, the quantum fluctuations in gravity (graviton) become long wavelength gravitational waves that produced the B-mode we see.

Wasnt B-mode polarization detected last year?
Yes - but a different kind. Last summer the 10-meter South Pole Telescope announced the first evidence for B-mode polarization in the CMB on arcminute scales which arises from the lensing, or bending of light, by gravitational attraction of structures formed in the relatively recent universe. Recently a second telescope, Polarbear, has also detected this effect. Our data sees this lensing effect too, but what is critical is that we see strong B-mode polarization at the much larger angular scales--2 to 4 degrees on the sky--where lensing is a tiny effect but where inflationary gravitational waves are expected to peak.
Didnt Planck find that r < 0.11? Do your experiments disagree?
Our measurements dont disagree. Constraints on the gravitational-wave background level r reported from Planck and previous experiments are not from measurements of B-mode polar

Spontaneous Discussion on Cosmology results

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Op maandag 17 maart 2014 17:46 schreef Jorwol het volgende:

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Ik wilde net hetzelfde zeggen: ik snap er geen kloot van maar het is wel interessant

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Op maandag 17 maart 2014 23:38 schreef Parafernalia het volgende:
Kan iemand in Jip & Janneke-taal uitleggen waarom dit een aanwijzing zou zijn voor een multiversum (een oneindig aantal zelfs?)?

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Op dinsdag 18 maart 2014 00:01 schreef Parafernalia het volgende:

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Ja maar waarom dan?