the CMB cold spot problem in review

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the CMB cold spot problem in review

#1

Post by notFritzArgelander » Wed Feb 12, 2020 9:17 pm

It's a long article. Can translate on an ad hoc basis sp questions are welcome.

BTW I'm not a fan of the multiverse explanation, so there's that.

https://physicsworld.com/a/the-enduring ... cold-spot/
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#2

Post by pakarinen » Wed Feb 12, 2020 9:57 pm

Conformal Cyclic Cosmology. A brane bump?
If you don't understand your noise, you cannot reliably extract a meaningful signal.
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#3

Post by helicon » Wed Feb 12, 2020 10:49 pm

I skimmed it at first and then read the first half of the article. Then I got interrupted by the plumber visiting, he's still here so I won't get back to it for awhile. Leaky faucet that I couldn't fix.
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#4

Post by notFritzArgelander » Wed Feb 12, 2020 11:22 pm

pakarinen wrote:
Wed Feb 12, 2020 9:57 pm
Conformal Cyclic Cosmology. A brane bump?
Or a burry brane?
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#5

Post by GCoyote » Thu Feb 13, 2020 1:48 pm

helicon wrote:
Wed Feb 12, 2020 10:49 pm
I skimmed it at first and then read the first half of the article. Then I got interrupted by the plumber visiting, he's still here so I won't get back to it for awhile. Leaky faucet that I couldn't fix.
I hate it when real life interferes with me reading more stuff that I won't understand. :shock:
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#6

Post by Michael131313 » Thu Feb 13, 2020 7:15 pm

Thanks n_FA. Long, as you say, but pretty interesting.
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#7

Post by helicon » Thu Feb 13, 2020 7:25 pm

Finally finished the article.
It should come as no surprise then that researchers the world over have posited a number of theories regarding the CMB cold spot, and many studies are being done to uncover its origins. Some early explanations suggested that the cold spot could merely be foreground contamination (in the form of galactic dust and synchrotron radiation) from within the Milky Way, or the result of unusual celestial objects. But observations by the NRAO VLA Sky Survey (NVSS), the 2 Micron All-Sky Survey (2MASS) and the Sloan Digital Sky Survey (SDSS), along with detailed images from the Hubble Space Telescope, all showed no such objects.
OK, so there's that. The author chronologically reviews the available literature that has attempted to answer the question....however to date there are no slam dunk theories that can account for the cold spot.

Then...
As it stands, our current understanding of the CMB cold spot doesn’t lead us to any clear conclusions. Fully understanding it either requires much better observations, or a revision of our understanding of the universe. Hopefully, future observations from more advanced ground- and space-based telescopes can guide us towards a better explanation of this enigmatic scientific phenomenon.
The giant Magellan telescope, it seems, may play a role in getting a definitive answer.
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#8

Post by notFritzArgelander » Thu Feb 13, 2020 8:30 pm

This is a seriously troubling issue for the Standard Cosmology.

I've reviewed the few physical arguments in the piece and while they are simplified, they do not distort.

For it to have the least impact there needs to be a void and the closer the better. That seems to be getting ruled out pretty well by the existing surveys. All the proposed explanations have some problems. So I really don't have much to add. I have no clue.

More data needed.... :shrug:

The only thing I'm certain of is that the further out this anomaly is located, the more severe the consequences will be for the Standard Cosmology. Fans of multiverses (count me out of that one) need to hope that it's beyond the reach of the GMT or the JWST.
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#9

Post by pakarinen » Thu Feb 13, 2020 9:34 pm

I thought the void explanation had been discredited already.

Started working my way through an up-to-date intro cosmology text. I can't believe how much math I've forgotten. Oh well, Diff Eq didn't pay the mortgage all those years...
If you don't understand your noise, you cannot reliably extract a meaningful signal.
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#10

Post by notFritzArgelander » Thu Feb 13, 2020 9:53 pm

pakarinen wrote:
Thu Feb 13, 2020 9:34 pm
I thought the void explanation had been discredited already.
Only within limits of current observations. Also, if it's a dark matter void specifically, that's not ruled out.
Started working my way through an up-to-date intro cosmology text. I can't believe how much math I've forgotten. Oh well, Diff Eq didn't pay the mortgage all those years...
I'm calculating slowly. Trying to resist the urge to hang it up but it's tough. I find my reading comprehension of math is in good shape but calculation is painful. Maybe my threshold of pain tolerance has dropped? :lol:

What are you reading?
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#11

Post by chasmanian » Fri Feb 14, 2020 5:08 am

doesn't the CMB cold spot problem belong on this list?:

https://en.wikipedia.org/wiki/List_of_u ... in_physics
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#12

Post by notFritzArgelander » Fri Feb 14, 2020 5:18 am

chasmanian wrote:
Fri Feb 14, 2020 5:08 am
doesn't the CMB cold spot problem belong on this list?:

https://en.wikipedia.org/wiki/List_of_u ... in_physics
I think it is implicitly represented under the "large scale anisotropy" problem. Thus:
Is the universe at very large scales anisotropic, making the cosmological principle an invalid assumption? The number count and intensity dipole anisotropy in radio, NRAO VLA Sky Survey (NVSS) catalogue[41] is inconsistent with the local motion as derived from cosmic microwave background[42][43] and indicate an intrinsic dipole anisotropy. The same NVSS radio data also shows an intrinsic dipole in polarization density and degree of polarization[44] in the same direction as in number count and intensity. There are several other observation revealing large-scale anisotropy. The optical polarization from quasars shows polarization alignment over a very large scale of Gpc.[45][46][47] The cosmic-microwave-background data shows several features of anisotropy,[48][49][50][51] which are not consistent with the Big Bang model.
Reference [51] is particularly good. But it's only for math mavens.
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#13

Post by GCoyote » Fri Feb 14, 2020 12:45 pm

Random thought, do these deviations from homogeneity and isotropy point in the same general direction or are they also random in orientation, at least for those measurements were direction is a sensible property to consider.
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#14

Post by pakarinen » Fri Feb 14, 2020 1:31 pm

notFritzArgelander wrote:
Thu Feb 13, 2020 9:53 pm
What are you reading?
Vittorio. "Cosmology" in CRC series.

Related to this thread: Trying to remember the reference for a paper on local bulk flow and the (lack of a) void. Pretty sure it was arxiv.org but I can't find my book mark now.
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#15

Post by notFritzArgelander » Sat Feb 15, 2020 5:13 am

GCoyote wrote:
Fri Feb 14, 2020 12:45 pm
Random thought, do these deviations from homogeneity and isotropy point in the same general direction or are they also random in orientation, at least for those measurements were direction is a sensible property to consider.
Let me look again. Of course the cold spot is special. I'm not sure the other deviations are consistent.
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#16

Post by notFritzArgelander » Sat Feb 15, 2020 5:58 am

GCoyote wrote:
Fri Feb 14, 2020 12:45 pm
Random thought, do these deviations from homogeneity and isotropy point in the same general direction or are they also random in orientation, at least for those measurements were direction is a sensible property to consider.
Ive gone back and looked at this reference in detail...

https://academic.oup.com/mnras/article/ ... 11/1247401

Independent of the cold spot, the octuple and quadrupole anisotropy moments do align and point in the direction of the Virgo Cluster. So that's what they were detecting with WMAP. The cold spot is much more troubling.
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#17

Post by notFritzArgelander » Sat Feb 15, 2020 7:15 am

pakarinen wrote:
Fri Feb 14, 2020 1:31 pm
notFritzArgelander wrote:
Thu Feb 13, 2020 9:53 pm
What are you reading?
Vittorio. "Cosmology" in CRC series.

Related to this thread: Trying to remember the reference for a paper on local bulk flow and the (lack of a) void. Pretty sure it was arxiv.org but I can't find my book mark now.
Here's the first measurement from WMAP data

https://academic.oup.com/mnras/article/ ... 17/2908436

A popular summary of the current state

https://www.forbes.com/sites/brucedormi ... 2d14cd4e0a

Note:
“If the bulk flow continues well beyond the Shapley Concentration then there’s something fundamental that we really don’t understand,” said Tully. “But we’re not going to know for sure until we get peculiar velocities of a factor of three farther in distance.”
and
it’s currently difficult to detect peculiar velocities beyond a distance of some 400 million light years. But when the LSST (Large Synoptic Survey Telescope) sees first light in 2021, he and colleagues speculate that if errors can be reduced, then a detection of the cosmos’ bulk flow out to some three billion light years might just be possible.
Then there's this recent item which is low significance https://www.aanda.org/articles/aa/full_ ... 73-19.html
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#18

Post by metastable » Sun Feb 16, 2020 6:34 am

are there any implications for noether’s theorem?
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#19

Post by notFritzArgelander » Sun Feb 16, 2020 7:04 am

metastable wrote:
Sun Feb 16, 2020 6:34 am
are there any implications for noether’s theorem?
Not yet, certainly. The statistics for the cold spot are under whelming. There is a ~2% chance that it's just a fluke. Unlikely but not good enough to claim a discovery. WMAP gave a 1.85% chance that it's a fluctuation and PLANCK gave a similar result so the prior doubt about it being an artifact of WMAP was set aside.

It's good enough to cause concern but the void hypothesis has not been falsified..... yet, if ever. The observations from the LSST are essential to establish whether or not a complete or partial (dark matter only) void is the cause. These are the observation programs most at risk from intrusive satellite constellations, BTW.

Although the cold spot seems real, there needs to be a distance determination (LSST) to asses whether it is near and due to a void or distant and primordial.

For there to be an implication for Noether's Theorem there would need to be
1) a discovery level confidence interval (1 in 3.6 million chance of it being a statistical fluke)
2) the distance would have to be at the CMB horizon (46 B lyr away in comoving coordinate, 13.B yr look back time) ruling out a void

Then Noether's Theorem would be empirically falsified. We would then not know how to do physics and would have to rethink the foundations of the enterprise.

I rather doubt that's going to happen.
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#20

Post by notFritzArgelander » Sun Feb 16, 2020 7:44 am

pakarinen wrote:
Fri Feb 14, 2020 1:31 pm
notFritzArgelander wrote:
Thu Feb 13, 2020 9:53 pm
What are you reading?
Vittorio. "Cosmology" in CRC series.
I just took a peek at it on Amazon. It looks to be quite nice and even tempting....

The most recent monograph I have is the 1993 update of Peebles Physical Cosmology.
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