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View Full Version : Isotropy or Anisotropy...that is the question,WMAP 9 yr data.



trinitree88
2017-Oct-27, 05:05 PM
When things are smooth and homogeneous, they are isotropic, appearing the same in all directions. When they are not....that's anisotropic. WMAP is the acronym for the Wilkinson Microwave Anisotropy Probe, a satellite launched to measure how isotropic the microwaves left over from the putative Big Bang are. It has had a series of releases as data accumulates over the years, and the first releases were pretty isotropic as expected...WMAP 3,WMAP 5. But, the 9 year data shows an anisotropic signal @ the same confidence level, according to the authors. Something's up.

SEE:https://arxiv.org/abs/1710.09641

pete

George
2017-Oct-28, 07:14 PM
There were several sentences I understood. Power entropy and Eigen values were a distracting blur to the picture they are painting. The faintness of the anisotropy is well known perhaps from Boomerang on, so what's new with their take on WMAP9 data? [If the anistropy itself has changed much since WMAP5, then the debunked 6000 yr. universe hypothesis gets debunked again since this would be way too long. *wink*]

Shaula
2017-Oct-28, 07:58 PM
There were several sentences I understood. Power entropy and Eigen values were a distracting blur to the picture they are painting. The faintness of the anisotropy is well known perhaps from Boomerang on, so what's new with their take on WMAP9 data?
The signals are still weak. Their study focuses on studying alignment in higher order modes which is something that is pretty hard to do. There are serious overfitting issues in this domain and a risk that imperfect corrections for lower order multipole signals leads to spurious signals in higher order moments. The paper provides some interesting work on bounding the potential anisotropies though.

George
2017-Oct-29, 05:23 PM
Allowing for some guessing, what are the implications from this? Greater or leser anisotropy, perhaps? Polarization tweaks?

Shaula
2017-Oct-29, 06:55 PM
Allowing for some guessing, what are the implications from this? Greater or leser anisotropy, perhaps? Polarization tweaks?
It is difficult to work out why there would be very high order structure but no lower order structure so I am not sure it is easy to say. Any anisotropy is interesting but these alignments feel more like a consequence of processing or modelling at first sight. That may be wrong, but alternative explanations would have to cover off the apparent cancellation of all of the lower order aligned multipole anisotropies.

George
2017-Oct-30, 01:42 PM
It is difficult to work out why there would be very high order structure but no lower order structure so I am not sure it is easy to say. .That's an interesting point. Perhaps more will follow from WMAP9 data.

wd40
2017-Oct-30, 08:27 PM
In 2 September 2009, the New Scientist stated: "The European Space Agency's recently launched PLANCK space telescope might settle the issue when it makes the most sensitive maps yet of the CMB. Until then, the Axis of Evil continues to terrorise us".

Has this this new paper "Testing isotropy of cosmos with WMAP and PLANCK data" done anything to allay, exacerbate or be neutral about this so-called 'terror'?

Shaula
2017-Oct-30, 08:49 PM
In 2 September 2009, the New Scientist stated: "The European Space Agency's recently launched PLANCK space telescope might settle the issue when it makes the most sensitive maps yet of the CMB. Until then, the Axis of Evil continues to terrorise us".

Has this this new paper "Testing isotropy of cosmos with WMAP and PLANCK data" done anything to allay, exacerbate or be neutral about this so-called 'terror'?
As the paper states, the low order anisotropy is still present but at a low confidence level. The headline is rather tongue in cheek, there is nothing scary or worrying about anisotropy maps. It is just data. If the data doesn't fit current models well or causes us to adjust them then we have learned something. If it doesn't then the models hold. Neither result is worrying, frightening or evil. If anything finding something new is exciting and positive, it is how science moves on. No one is sitting in a little lab shaking at the thought that a model might require replacing or updating.