B The Universe is now closed and curved?

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I read a news article about a recent study into the cmb which suggests that the universe is now been discovered to be closed and curved. Not seen anything here so am assuming it’s just another misinterpreted pop science piece. Anyone know what the article is talking about please?

please see this Article
 

256bits

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99.8% confidence it says in the article.
See below from the Live Science article ( mentioned if your link ), which is a lot better.

Melchiorri pointed out that his team's interpretation isn't conclusive. According to the group's calculations, the Planck data point to a closed universe with a standard deviation of 3.5 sigma (a statistical measurement that means about 99.8% confidence that the result isn't due to random chance). That's well short of the 5 sigma standard physicists usually look for before calling an idea confirmed.
More work to be done to confirm or disprove.
 

kimbyd

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99.8% confidence it says in the article.
See below from the Live Science article ( mentioned if your link ), which is a lot better.



More work to be done to confirm or disprove.
I'd say something different here: the single result of any one study should not be taken as definitive. Especially for more unexpected results. Always wait for confirmation, regardless of the quoted accuracy.

That said, I'll see if I can't find the scientific paper and see if there's anything more specific I can say.
 

kimbyd

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Ugh. It's a Nature article. That means no preprint. Very disappointing.

According to the abstract, however, it sounds reasonable. What they're claiming is that if they take the Plank 2018 curvature estimate seriously, it also resolves a number of other issues with the data. Without access to the full paper I can't say much, but it is certainly compelling.

The next questions I would like to see answered are related to how this result fits with nearby data. Does it, for instance, resolve the tension in the Hubble parameter between the CMB and nearby observations?

Side note on a theoretical point: many theories for the very early universe actually require a slightly closed universe, but allow the curvature to be so incredibly tiny that we couldn't measure it. If this result holds, it could provide some interesting hints as to what happened in the very early universe, e.g. during inflation.
 
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I read a news article about a recent study into the cmb which suggests that the universe is now been discovered to be closed and curved.
"Discovered" is an overstatement. It's an open question that is still being debated. Certainly a statement in a newspaper headline should not be taken as an accurate reflection of the current state of the actual science.
 

WWGD

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When will be the next planck data release ? I think that with the James Webb and by making more and more measurements things will be clear.
 

Buzz Bloom

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In the article version I looked at (see below) there were many uses of the word tension. I was unable to find what this word means in these contexts. I would much appreciate someone explaining what the usage of tension in the article means.

The following are a few examples.
Before evaluating the tensions of the PL18 results with independent cosmological observables, we first check whether the PL18 power spectra can provide an unbiased and reliable estimate of the curvature of the Universe.
When log 10 I I is positive, then two datasets are in agreement, whereas they are in tension if this parameter is negative.
A second tension is present between PL18 power spectra and the constraints on the lensing potential derived from the four-point function of Planck CMB maps39 (hereafter, called CMB lensing).
This tension is also present in the PL18 release 2 , and the inclusion of the A lens parameter removes this difference.
Even assuming these data points to be independent, the increase in χ2 when curvature is varied suggests there is tension at the 95% CL, while there is no significant tension in the case of flatness.
Fig. 4 | Tension with BAO.
Fig. 5 | Tension with CMB lensing.
Fig. 6 | Tension with Cosmic shear measurements.









 

PAllen

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It simply means possible disagreement at some level of confidence. It is a general English usage, not a technical term in all of your examples.
 

timmdeeg

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No cost here.

Planck evidence for a closed Universe and a possible crisis for cosmology
Eleonora Di Valentino1, Alessandro Melchiorri2* and Joseph Silk3,4,5
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 param-eters 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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You have to pay for it, at least it insists I must.
I just checked and it's still available to me- I don't think I have anything that would give me free access to anything Nature.

There's a pop-up that says "Online access to this article has been provided by Springer Nature SharedIt."

I Googled the paper's title and Google game me the link.
 

Buzz Bloom

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It simply means possible disagreement at some level of confidence. It is a general English usage, not a technical term in all of your examples.
Hi Paul:

Thank you much for your reply to my question. When I looked at some online dictionaries, I get that several of the "English usage" definitions for "tension" involve a sense of conflict or disagreement, but the definition particulars are much different than the article usage, and the difference seems to me to be quite technical.
In particular, the usage in the article is specifically related to the technical concept of "level of confidence". So I am left with the interpretation that the article usage is a new technical metaphor, or at least one I have not seen before.

Regards,
Buzz
 

Ibix

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In particular, the usage in the article is specifically related to the technical concept of "level of confidence". So I am left with the interpretation that the article usage is a new technical metaphor, or at least one I have not seen before.
I agree with @PAllen here. It's just being used in the sense that there's a cluster of "high" results which all seem perfectly plausible and a cluster of "low" results that also seem perfectly plausible, so our beliefs about the correct value are pulled in two directions. And academic fights can get surprisingly nasty. So I think it's a purely metaphorical tension between two sets of beliefs.
 

phinds

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Hi Paul:

Thank you much for your reply to my question. When I looked at some online dictionaries, I get that several of the "English usage" definitions for "tension" involve a sense of conflict or disagreement, but the definition particulars are much different than the article usage, and the difference seems to me to be quite technical.
I'm puzzled by the lack of what I definitly consider to be an appropriate alternate definition, specifically the one @PAllen provided.
 

PAllen

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I just checked and it's still available to me- I don't think I have anything that would give me free access to anything Nature.

There's a pop-up that says "Online access to this article has been provided by Springer Nature SharedIt."

I Googled the paper's title and Google game me the link.
I get no such pop up, and the insistence that I rent, buy, or subscribe. Nothing I try gets around it. It could be location specific.

[edit: tried it on a slower computer and see a very brief pop up that says "we are unable to provide full access at this time", and then redirects to the abstract page, which shows only pay options. Again, I suspect only some regions are allowed the full access from Nature. Thank ... for slow computers].
 
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kimbyd

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Looking through the paper, here are my main take-aways:

1) They do do an analysis with a lot of different data sets, so this paper really is pretty comprehensive with its analysis.
2) When they allow for a closed universe, some of the data sets seem to agree with one another quite a bit more. Others do not.

So basically this paper suggests the following possibilities:
1) Our universe is closed, but we're still missing something else that will fix the remaining discrepancies.
2) This paper is barking up the wrong tree, and something else entirely solves these discrepancies.

All in all, this paper cannot be taken as definitive on its face, simply because many discrepancies remain. This is in addition to the usual advice of waiting for confirmation. The paper is certainly suggestive that a closed universe may be a possibility, but more measurements are needed.
 

timmdeeg

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All in all, this paper cannot be taken as definitive on its face, simply because many discrepancies remain. This is in addition to the usual advice of waiting for confirmation. The paper is certainly suggestive that a closed universe may be a possibility, but more measurements are needed.
Having read the paper do you think there could be a bridge to another discrepancy discussed recently, the so called Hubble tension?
 

kimbyd

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Having read the paper do you think there could be a bridge to another discrepancy discussed recently, the so called Hubble tension?
The Hubble tension is largely unaffected by this analysis (this is clearest in Fig. 8). From my reading of the paper, it looks like this tension is the primary remaining tension between the nearby Hubble parameter measurements and other cosmological data.
 

timmdeeg

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Ok, thanks.
 

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