Harvard-Smithsonian B-Mode observation confirmed

Study matter and its motion through spacetime...

Moderators: Calilasseia, ADParker

Re: Harvard-Smithsonian B-Mode observation confirmed

#161  Postby Spinozasgalt » Jan 30, 2015 11:21 pm

The existence of dust fits with most versions of moral realism, so I'm taking this as confirmation of my theory.
When the straight and narrow gets a little too straight, roll up the joint.
Or don't. Just follow your arrow wherever it points.

Kacey Musgraves
User avatar
Spinozasgalt
RS Donator
 
Name: Jennifer
Posts: 18152
Age: 32
Male

Country: Australia
Australia (au)
Print view this post

Ads by Google


Re: Harvard-Smithsonian B-Mode observation confirmed

#162  Postby hackenslash » Jan 31, 2015 7:15 am

:lol:
User avatar
hackenslash
THREAD STARTER
 
Name: The Other Sweary One
Posts: 21413
Age: 50
Male

Country: Republic of Mancunia
Print view this post

Re: Harvard-Smithsonian B-Mode observation confirmed

#163  Postby Pulsar » Feb 02, 2015 11:44 pm

Full paper: A Joint Analysis of BICEP2/Keck Array and Planck Data

This is the killer plot:

Image

The black dots with error bars show the original BICEP/Keck results, the purple dots with error bars show the corrected results after subtracting the dust contribution found by Planck. The red line is the B-mode polarization that’s expected from gravitational lensing alone (so without primordial gravitational waves). Clearly, the new results show no hint of primordial gravitational waves, except for a slight (not statistically significant) excess signal around multipoles of order 200.

So for now, the champagne can be put back in the fridge. It's important to emphasize though that the BICEP experiment only looked at a small patch of the sky and at one particular frequency. We'll have to wait and see what the other ongoing experiments will reveal.
"The longer I live the more I see that I am never wrong about anything, and that all the pains that I have so humbly taken to verify my notions have only wasted my time." - George Bernard Shaw
User avatar
Pulsar
 
Posts: 4618
Age: 42
Male

Country: Belgium
Belgium (be)
Print view this post

Re: Harvard-Smithsonian B-Mode observation confirmed

#164  Postby newolder » Jul 17, 2018 6:43 pm

The 2018 release of the analysis of Planck's observations is out: https://www.cosmos.esa.int/documents/38 ... ts_L10.pdf

Improvements on the error bars almost remove B-modes completely.
15 March 2018

ABSTRACT

We report on the implications for cosmic inflation of the 2018 release of the Planck cosmic microwave background (CMB) anisotropy measure- ments. The results are fully consistent with those reported using the data from the two previous Planck cosmological releases, but have smaller uncertainties thanks to improvements in the characterization of polarization at low and high multipoles. Planck temperature, polarization, and lensing data determine the spectral index of scalar perturbations to be ns =0.9649±0.0042 at 68% CL.We find no evidence for a scale dependence of ns, either as a running or as a running of the running. The Universe is found to be consistent with spatial flatness with a precision of 0.4 % at 95 % CL by combining Planck with a compilation of BAO data. The Planck 95 % CL upper limit on the tensor-to-scalar ratio, r0.002 < 0.10, is further tightened by combining with the BICEP2/Keck Array BK14 data to obtain r0.002 < 0.064.

...more at link...


Neil Turok et al will be pleased. :coffee:
Geometric forgetting gives me loops. - Nima A-H
User avatar
newolder
 
Name: Albert Ross
Posts: 6506
Age: 8
Male

Country: Feudal Estate number 9
Print view this post

Re: Harvard-Smithsonian B-Mode observation confirmed

#165  Postby felltoearth » Jul 17, 2018 7:16 pm

Sorry, what is meant by spatial flatness here and how is it relevant? Asking for a dumb friend.
"Walla Walla Bonga!" — Witticism
User avatar
felltoearth
 
Posts: 11781
Age: 52

Canada (ca)
Print view this post

Re: Harvard-Smithsonian B-Mode observation confirmed

#166  Postby newolder » Jul 17, 2018 7:46 pm

Angles in triangles (on the largest measurable scales - i.e. out to the surface of last scattering where the CMB radiation was emitted) add up to π radians.

It's relevance is that it helps determine the "kind" of universe we occupy - flat, positive or negatively curved. The obs. show that (at large distances from matter and black holes etc.) it's very, very near flat.

Edit to remove the /2 :doh:
Geometric forgetting gives me loops. - Nima A-H
User avatar
newolder
 
Name: Albert Ross
Posts: 6506
Age: 8
Male

Country: Feudal Estate number 9
Print view this post

Re: Harvard-Smithsonian B-Mode observation confirmed

#167  Postby felltoearth » Jul 17, 2018 7:56 pm

Very interesting, thanks!
"Walla Walla Bonga!" — Witticism
User avatar
felltoearth
 
Posts: 11781
Age: 52

Canada (ca)
Print view this post

Ads by Google


Re: Harvard-Smithsonian B-Mode observation confirmed

#168  Postby Calilasseia » Jul 17, 2018 7:57 pm

Here, spatial flatness means that space unoccupied by massive objects is nearly or completely Euclidean. The familiar geometry of Euclid applies thereto. There's no space-time curvature to worry about. Which makes life simple, due to the fact that the metric tensor for a Eucidean space is the identity matrix in N dimensions.

The moment space has curvature, that metric tensor becomes much more complicated, and much more difficult to work with in a practical application.

Furthermore, said flatness applies not only on the small scale, but the large scale too.

The reason spatial flatness is important, is that inflationary cosmologies all predict that the resulting spacetime generated is Euclidean or nearly so, and any significant departure from Euclidean flatness would hole all of those cosmologies below the waterline, so to speak.
Signature temporarily on hold until I can find a reliable image host ...
User avatar
Calilasseia
RS Donator
 
Posts: 22011
Age: 57
Male

Country: England
United Kingdom (uk)
Print view this post

Re: Harvard-Smithsonian B-Mode observation confirmed

#169  Postby newolder » Jul 17, 2018 8:12 pm

The relevant wiki page ends with:
...
Paul Steinhardt, one of the founding fathers of inflationary cosmology, has recently become one of its sharpest critics. He calls 'bad inflation' a period of accelerated expansion whose outcome conflicts with observations, and 'good inflation' one compatible with them: "Not only is bad inflation more likely than good inflation, but no inflation is more likely than either [...]
Roger Penrose considered all the possible configurations of the inflaton and gravitational fields. Some of these configurations lead to inflation [...] Other configurations lead to a uniform, flat universe directly – without inflation. Obtaining a flat universe is unlikely overall. Penrose's shocking conclusion, though, was that obtaining a flat universe without inflation is much more likely than with inflation – by a factor of 10 to the googol (10 to the 100) power!"[4][116] Together with Anna Ijjas and Abraham Loeb, he wrote articles claiming that the inflationary paradigm is in trouble in view of the data from the Planck satellite.[144][145] Counter-arguments were presented by Alan Guth, David Kaiser, and Yasunori Nomura[146] and by Andrei Linde,[147] saying that "cosmic inflation is on a stronger footing than ever before".[146]


Theoretical concerns in cosmology are debated hotly...
Geometric forgetting gives me loops. - Nima A-H
User avatar
newolder
 
Name: Albert Ross
Posts: 6506
Age: 8
Male

Country: Feudal Estate number 9
Print view this post

Re: Harvard-Smithsonian B-Mode observation confirmed

#170  Postby newolder » Jul 17, 2018 9:49 pm

ESA write up: http://www.esa.int/Our_Activities/Space ... oth_worlds

No mention of the tension due to the Hubble constant discrepancy between Planck obs. and supernova data though there is this:
The combined new data from the Gaia and Hubble Space Telescope data are in serious conflict with the Cosmic Microwave Background data," said Planck team member George Efstathiou of the Kavli Institute for Cosmology in Cambridge. The results fuel the mismatch between measurements for the expansion rate of the nearby universe, and those of the distant, primeval universe—before stars and galaxies even existed.
...more at link below.

http://www.dailygalaxy.com/my_weblog/20 ... unive.html
Geometric forgetting gives me loops. - Nima A-H
User avatar
newolder
 
Name: Albert Ross
Posts: 6506
Age: 8
Male

Country: Feudal Estate number 9
Print view this post

Re: Harvard-Smithsonian B-Mode observation confirmed

#171  Postby felltoearth » Jul 17, 2018 10:09 pm

:cheers:
"Walla Walla Bonga!" — Witticism
User avatar
felltoearth
 
Posts: 11781
Age: 52

Canada (ca)
Print view this post

Re: Harvard-Smithsonian B-Mode observation confirmed

#172  Postby newolder » Oct 18, 2018 4:04 pm

Latest arxiv link on primordial gravitational wave measurements.
(Draft As accepted by PRL)

We present results from an analysis of all data taken by the BICEP2/Keck CMB polarization experiments up to and including the 2015 observing season. This includes the first Keck Array obser- vations at 220 GHz and additional observations at 95 & 150 GHz. The Q/U maps reach depths of 5.2, 2.9 and 26 μKcmb arcmin at 95, 150 and 220 GHz respectively over an effective area of ≈ 400 square degrees. The 220 GHz maps achieve a signal-to-noise on polarized dust emission approximately equal to that of Planck at 353GHz. We take auto- and cross-spectra between these maps and publicly available WMAP and Planck maps at frequencies from 23 to 353 GHz. We evaluate the joint likeli- hood of the spectra versus a multicomponent model of lensed-ΛCDM+r+dust+synchrotron+noise. The foreground model has seven parameters, and we impose priors on some of these using external information from Planck and WMAP derived from larger regions of sky. The model is shown to be an adequate description of the data at the current noise levels. The likelihood analysis yields the constraint r0.05 < 0.07 at 95% confidence, which tightens to r0.05 < 0.06 in conjunction with Planck temperature measurements and other data. The lensing signal is detected at 8.8σ significance. Running maximum likelihood search on simulations we obtain unbiased results and find that σ(r) = 0.020. These are the strongest constraints to date on primordial gravitational waves.

...
The constraint on primordial gravitational waves parametrized by tensor to scalar ratio r is improved to r0.05 < 0.062 (95%), disfavoring the important class of inflationary models represented by a φ potential[4, 5].
...
Geometric forgetting gives me loops. - Nima A-H
User avatar
newolder
 
Name: Albert Ross
Posts: 6506
Age: 8
Male

Country: Feudal Estate number 9
Print view this post

Previous

Return to Physics

Who is online

Users viewing this topic: No registered users and 1 guest