Planck analysis closes universe

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Planck analysis closes universe

#1  Postby newolder » Nov 06, 2019 9:22 am

Published in Nature Astronomy:
Planck evidence for a closed Universe and a possible crisis for cosmology

Abstract
The recent Planck Legacy 2018 release has confirmed the presence of an enhanced lensing amplitude in cosmic microwave background power spectra compared with that predicted in the standard Λ cold dark matter model, where Λ is the cosmological constant. A closed Universe can provide a physical explanation for this effect, with the Planck cosmic microwave background spectra now preferring a positive curvature at more than the 99% confidence level. Here, we further investigate the evidence for a closed Universe from Planck, showing that positive curvature naturally explains the anomalous lensing amplitude, and demonstrating that it also removes a well-known tension in the Planck dataset concerning the values of cosmological parameters derived at different angular scales. We show that since the Planck power spectra prefer a closed Universe, discordances higher than generally estimated arise for most of the local cosmological observables, including baryon acoustic oscillations. The assumption of a flat Universe could therefore mask a cosmological crisis where disparate observed properties of the Universe appear to be mutually inconsistent. Future measurements are needed to clarify whether the observed discordances are due to undetected systematics, or to new physics or simply are a statistical fluctuation.


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ETA : Also @ New Scientist article
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Re: Planck analysis closes universe

#2  Postby Macdoc » Nov 06, 2019 11:32 am

Branes then make sense :popcorn:

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Re: Planck analysis closes universe

#3  Postby newolder » Nov 06, 2019 11:40 am

Until future measurements provide confirmation of this single experiment, spoonfuls of systematic/statistical salt are the appropriate seasoning.
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Re: Planck analysis closes universe

#4  Postby Macdoc » Nov 06, 2019 12:16 pm

front loaders full perhaps
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Re: Planck analysis closes universe

#5  Postby CdesignProponentsist » Nov 06, 2019 8:37 pm

So where are they placing the upper limit for the size of the universe?
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Re: Planck analysis closes universe

#6  Postby Spearthrower » Nov 06, 2019 8:58 pm

CdesignProponentsist wrote:So where are they placing the upper limit for the size of the universe?


Contained within the glint of Jesus' eye.
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Re: Planck analysis closes universe

#7  Postby Spearthrower » Nov 06, 2019 8:59 pm

newolder wrote:*snippity snip*


Can you unpack this a bit Newolder?

I have always had a perhaps irrational assumption that the universe must be closed.
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Re: Planck analysis closes universe

#8  Postby newolder » Nov 06, 2019 9:04 pm

If it is positively curved hereabouts then what reason could prevent flatness and/or negative curvature somewhere over the ever expanding horizon (>> 40 billion light years)? I'd guess that the upper limit to the "size" of the universe remains infinite and just as difficult to disprove its infiniteness at this stage...
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Re: Planck analysis closes universe

#9  Postby newolder » Nov 06, 2019 9:14 pm

Spearthrower wrote:
newolder wrote:*snippity snip*


Can you unpack this a bit Newolder?

I have always had a perhaps irrational assumption that the universe must be closed.


The Friedmann-Robertson-Walker (FRW)* solutions to the Einstein equations were derived a while back but to paraphrase, in the absence of a cosmological constant (cc) and dependent upon the matter content, the curvature of the metric could be positive (closed, like a sphere), negative (open, like a saddle) or 0 (flat, like an apartment :lol: ).

A small and positive cc with critical matter content is also open (this is the current model used by e.g. the Planck consortium in all studies except this latest revelation). A small and positive cc in a closed universe will be an acceleratedly expanding sphere, I think, but I could be wrong here...

* Large-ish pdf on the background to FRW cosmology here where the geometry for the various matter contents (Omega0) is shown as pictures on the 5th page...
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Re: Planck analysis closes universe

#10  Postby Spearthrower » Nov 06, 2019 9:41 pm

Ahh yes, that helps ring some bells, cheers.
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Re: Planck analysis closes universe

#11  Postby Spearthrower » Nov 06, 2019 9:44 pm

newolder wrote:A small and positive cc in a closed universe will be an acceleratedly expanding sphere, I think, but I could be wrong here...


Presumably small variations in early conditions coupled with trillions of years of gravitational interactions could warp that the universe into a decidedly unspherical shape from the perspective of Yahweh and Vishnu.
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Re: Planck analysis closes universe

#12  Postby newolder » Nov 06, 2019 9:54 pm

Spearthrower wrote:
newolder wrote:A small and positive cc in a closed universe will be an acceleratedly expanding sphere, I think, but I could be wrong here...


Presumably small variations in early conditions coupled with trillions of years of gravitational interactions could warp that the universe into a decidedly unspherical shape from the perspective of Yahweh and Vishnu.


After trillions upon trillions upon (you get the picture) of years, the last things around will be humongous black holes with very low temperatures evaporating into the empty coldness and any "early time" variations will be completely smoothed out.

I do not know if the cc is truly constant in such vacuous conditions, so that's where I got my earlier posted notion that anything "could" be possible at very late time/very great distance. I leave it to the Penroses, Steinhardts & Turoks and etc. of this world to sort this near-vacuum state into proper calculable models though...
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Re: Planck analysis closes universe

#13  Postby Spearthrower » Nov 06, 2019 10:32 pm

newolder wrote:
After trillions upon trillions upon (you get the picture) of years, the last things around will be humongous black holes with very low temperatures evaporating into the empty coldness and any "early time" variations will be completely smoothed out.


Right, but that doesn't mean the shape of the universe would actually be spherical, though, does it? It could be both isotropic and a shape that anyone but a god would describe as 'fucking weird'.
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Re: Planck analysis closes universe

#14  Postby newolder » Nov 06, 2019 10:55 pm

Spearthrower wrote:
newolder wrote:
After trillions upon trillions upon (you get the picture) of years, the last things around will be humongous black holes with very low temperatures evaporating into the empty coldness and any "early time" variations will be completely smoothed out.


Right, but that doesn't mean the shape of the universe would actually be spherical, though, does it? It could be both isotropic and a shape that anyone but a god would describe as 'fucking weird'.


I have difficulty imagining what a 3-sphere actually looks like.

In mathematics, a 3-sphere, or glome, is a higher-dimensional analogue of a sphere. It may be embedded in 4-dimensional Euclidean space as the set of points equidistant from a fixed central point. ... A 3-sphere is an example of a 3-manifold and an n-sphere.


But I imagine an infinite universe doesn't look like that at all. :scratch:
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Re: Planck analysis closes universe

#15  Postby Spearthrower » Nov 06, 2019 11:04 pm

newolder wrote:But I imagine an infinite universe doesn't look like that at all. :scratch:


Fair enough - you're not Vishnu, after all.

It's kind of hard by default to imagine what a universe looks like from the outside.
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Re: Planck analysis closes universe

#16  Postby hackenslash » Nov 07, 2019 8:48 am

Interesting.

I talk a bit about curvature and the shape of the universe here:

https://www.hackenslash.co.uk/2016/03/b ... art-i.html

Well worth noting - as newolder alluded to - that positive curvature measured locally doesn't rule out the possibility that space is flat or even open on larger scales. This observation aside, the universe has been measured to be remarkably flat on the largest scales we've been able to measure, with no curvature at all to within very small error bars.

Also, a 3-sphere isn't the only closed solution available. A 4-torus is also a potential solution.
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Re: Planck analysis closes universe

#17  Postby Spearthrower » Nov 07, 2019 8:51 am

hackenslash wrote:A 4-torus is also a potential solution.


Only if the ineffable is trying to fuck with us!

Physics classes in 20 years: Ok, so over the course of the next 3 years, we're all going to try and wrap our heads around a 4 dimensional torus. Yes, that's all we'll be doing. :lol:
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Re: Planck analysis closes universe

#18  Postby newolder » Nov 07, 2019 8:55 am

Spearthrower wrote:
newolder wrote:But I imagine an infinite universe doesn't look like that at all. :scratch:


Fair enough - you're not Vishnu, after all.

'Now I am become Deaf, the destroyer of words.' is probably the closest I get to being Vishnu.

It's kind of hard by default to imagine what a universe looks like from the outside.


Yes, that's kinda the thing about an infinite universe - it has neither an outside nor a centre.

"You are not at the centre of the Earth, that is not at the centre of Solar system, that is not at the centre of the Milky Way, that is not at the centre of the Universe, that has no centre." as some cosmologist or other once related.
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Re: Planck analysis closes universe

#19  Postby Spearthrower » Nov 07, 2019 8:58 am

newolder wrote:
"You are not at the centre of the Earth, that is not at the centre of Solar system, that is not at the centre of the Milky Way, that is not at the centre of the Universe, that has no centre." as some cosmologist or other once related.



"And you're a very naughty boy" he added with finality.
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Re: Planck analysis closes universe

#20  Postby newolder » Nov 07, 2019 9:02 am

hackenslash wrote:Interesting.

I talk a bit about curvature and the shape of the universe here:

https://www.hackenslash.co.uk/2016/03/b ... art-i.html

Well worth noting - as newolder alluded to - that positive curvature measured locally doesn't rule out the possibility that space is flat or even open on larger scales. This observation aside, the universe has been measured to be remarkably flat on the largest scales we've been able to measure, with no curvature at all to within very small error bars.

Also, a 3-sphere isn't the only closed solution available. A 4-torus is also a potential solution.


Indeed it is, and without ruling out an extra, large dimension to space the Steinhardt & Turok double Klein bottle comes into play too...
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