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Thread: Is non-baryonic dark matter created on the fly?

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    Is non-baryonic dark matter created on the fly?

    Would the following article:
    https://phys.org/news/2017-03-dark-i...-universe.html

    suggests non-baryonic dark matter is created on the fly over a long period of time?


    Thanks,
    philippeb8

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    Quote Originally Posted by philippeb8 View Post
    Would the following article:
    https://phys.org/news/2017-03-dark-i...-universe.html

    suggests non-baryonic dark matter is created on the fly over a long period of time?



    Thanks,
    philippeb8
    What this says to me is that in the early universe, the Dark Matter "halos" were small and dense. Whatever spiral structure moved around a smaller inner "object". Now, after ten times as long for mergers, and other gravitational interactions, the halos are more extended. Nothing about this article seems to imply that substantial amounts of dark matter is being created currently in the cosmos.
    Forming opinions as we speak

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    Quote Originally Posted by antoniseb View Post
    What this says to me is that in the early universe, the Dark Matter "halos" were small and dense. Whatever spiral structure moved around a smaller inner "object". Now, after ten times as long for mergers, and other gravitational interactions, the halos are more extended. Nothing about this article seems to imply that substantial amounts of dark matter is being created currently in the cosmos.
    Ok but it's still a possibility. Whether dark matter is spread around or created on the fly is yet to be determined.

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    i don't see any mention of the possibility of "on the fly" creation, you are just making things up
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    Quote Originally Posted by tusenfem View Post
    i don't see any mention of the possibility of "on the fly" creation, you are just making things up
    No they don't mention because they don't know for sure it but it is implied by extrapolation.

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    Quote Originally Posted by philippeb8 View Post
    No they don't mention because they don't know for sure it but it is implied by extrapolation.
    Not really. The article gives several reasons why this could be that are all more plausible than this idea. Mainly because other pieces of evidence strongly suggest that DM was around at least as far back as the nucleosynthetic era in similar proportions to those we now see.

    As they say in the article - the condensation time for DM is much greater than for baryonic matter. That is probably one of the strongest drivers.

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    Quote Originally Posted by Shaula View Post
    Not really. The article gives several reasons why this could be that are all more plausible than this idea. Mainly because other pieces of evidence strongly suggest that DM was around at least as far back as the nucleosynthetic era in similar proportions to those we now see.

    As they say in the article - the condensation time for DM is much greater than for baryonic matter. That is probably one of the strongest drivers.
    Ok thanks for the clarifications.

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    The paper (look at the first comment https://arxiv.org/ftp/arxiv/papers/1703/1703.04310.pdf ) refers to non-baryonic and non-relativistic dark matter.

    According to this paper, 10 billion years ago total calculated matter almost equalled observed visible matter while now (according to Lambda CDM and PLANCK data) total calculated matter almost equals observed visible matter * 2 * Pi.

    I'm not sure how far Lambda CDM goes back in time, although it seems that this paper shows the time going from from 0 (-10,000) years to 10,000 (now) years as the ratio of total calculated matter to observed visible matter goes from 1 to 2 * Pi.

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    Quote Originally Posted by philippeb8 View Post
    Would the following article:
    https://phys.org/news/2017-03-dark-i...-universe.html
    suggests non-baryonic dark matter is created on the fly over a long period of time?
    No, I don't think anyone suggests that. And saying something is possible isn't saying much.

    i think the major contributor to this effect is the fact that "these early discs were much more turbulent than the spiral galaxies we see in our cosmic neighbourhood." There were many more galaxy collisions and mergers going on in the early universe. I'm thinking these collisions disperse the dark matter, which only much later coalesces around the merged system.
    Everyone is entitled to his own opinion, but not his own facts.

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    Quote Originally Posted by LaurieAG View Post
    According to this paper, 10 billion years ago total calculated matter almost equalled observed visible matter while now (according to Lambda CDM and PLANCK data) total calculated matter almost equals observed visible matter * 2 * Pi.
    Which paper? The only ratios of matter types I see in the paper linked is for galaxies only - not the universe as a whole. Also where did the focus on pi come from and why?

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    Quote Originally Posted by Shaula View Post
    Which paper? The only ratios of matter types I see in the paper linked is for galaxies only - not the universe as a whole. Also where did the focus on pi come from and why?
    The paper claimed that galaxies 10 billion years ago had hardly any dark matter compared with galaxies observed today.

    The 2 * pi = (4.82% + 25.8%)/4.82% and comes from the matter type percentages from the Wikipedia page about the 2013 Planck data. I haven't seen any dark matter breakdowns based on galactic matter vs non galactic matter for the universe as a whole.

    https://en.wikipedia.org/wiki/Planck...3_data_release

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    Quote Originally Posted by LaurieAG View Post
    The paper claimed that galaxies 10 billion years ago had hardly any dark matter compared with galaxies observed today.
    Yup, the galaxies did. Not the universe. Just wanted to make sure that was clear. I wasn't sure you were saying that as you referred back to the Planck mission which was, of course, measuring universal abundance, not galactic.

    Quote Originally Posted by LaurieAG View Post
    The 2 * pi = (4.82% + 25.8%)/4.82% and comes from the matter type percentages from the Wikipedia page about the 2013 Planck data. I haven't seen any dark matter breakdowns based on galactic matter vs non galactic matter for the universe as a whole.
    Pi is not 3.17634... which is that it would be it that ratio were 2pi. The dark matter/visible matter ratios are not related to pi in any current theory. I don't know why you have suddenly related the two.

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    Quote Originally Posted by philippeb8 View Post
    Would the following article:
    https://phys.org/news/2017-03-dark-i...-universe.html

    suggests non-baryonic dark matter is created on the fly over a long period of time?
    For the record, this article contradicts the following one which says dark matter decays over time:
    https://phys.org/news/2016-12-physic...-universe.html

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    Quote Originally Posted by philippeb8 View Post
    For the record, this article contradicts the following one which says dark matter decays over time:
    https://phys.org/news/2016-12-physic...-universe.html
    Well, to be fair, that articles says that one component of dark matter seems to decay over time, and also says that component cannot be more than about 2% to 5% of the total amount of dark matter. Reading the actual paper (linked at the bottom of the article), I'd say that it's intriguing but far from conclusive.
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    Quote Originally Posted by Shaula View Post
    Pi is not 3.17634... which is that it would be it that ratio were 2pi. The dark matter/visible matter ratios are not related to pi in any current theory.
    The error is within 1.1% and I have been told (on another forum) that this error is also within the error bars of the Planck data and calculations. It's actually the total matter/visible matter ratio that I referred to.

    https://en.wikipedia.org/wiki/Planck...3_data_release
    On 21 March 2013, the European-led research team behind the Planck cosmology probe released the mission's all-sky map of the cosmic microwave background
    ...
    According to the team, the Universe is 13.7980.037 billion years old, and contains 4.820.05% ordinary matter, 25.80.4% dark matter and 691% dark energy.[25][26][27]
    I haven't seen any breakdowns on dark matter, inside and outside of galaxies, although I have seen a paper that claimed that the amounts of visible matter inside and outside of galaxies were equivalent. Recently it has been revealed that apparently dark matter is not as clumpy as the Planck team estimated, according to latest research by ESO, but they don't seem to make any distinction between dark matter inside or outside of galaxies either.

    http://www.space.com/34926-dark-matt...so-clumpy.html
    To see how dark matter is distributed in universe, the international team of researchers used data from the Kilo Degree Survey (KiDS) at the VLT Survey Telescope. This deep-sky survey looked at about 15 million galaxies in five patches of the southern sky, covering an area as big as 2,200 full moons (or 450 square degrees).
    I couldn't find anything with regards to the distribution of dark matter that didn't depend on galaxies so I would appreciate it if you could point me to any links that could clarify this.

    Quote Originally Posted by Shaula View Post
    I don't know why you have suddenly related the two.
    If you look in this forums (longest?) thread you will see that I have used this relation as evidence of a scientific consensus MIR (Mind Independent Reality) element (before it becomes part of the scientific consensus MDR) several times. http://forum.cosmoquest.org/showthre...-about-reality.
    Last edited by LaurieAG; 2017-Mar-19 at 06:18 AM.

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    Quote Originally Posted by LaurieAG View Post
    The error is within 1.1% and I have been told (on another forum) that this error is also within the error bars of the Planck data and calculations. It's actually the total matter/visible matter ratio that I referred to.
    Apologies on using the wrong ratio. I still don't see why you are relating the two. So the ratio is three and a bit? If you take the ratio of the Hubble Constant to the Power spectrum of curvature perturbations you get (within error bars) the Efimov factor. The sum of the Power spectrum of curvature perturbations and the Thomson scattering optical depth due to reionization is roughly pi. I am sure we could come up with all kinds of 'relationships' if we use more factors and play with units.

    Quote Originally Posted by LaurieAG View Post
    I couldn't find anything with regards to the distribution of dark matter that didn't depend on galaxies so I would appreciate it if you could point me to any links that could clarify this.
    Currently the only reliable way to see dark matter is to see light lensed by it. So most observational evidence involves galaxies. There are a number of simulations that map likely distributions as part of structure formation though. The Millennium Simulation was a project of this ilk, there may have been more recent versions.

    Quote Originally Posted by LaurieAG View Post
    If you look in this forums (longest?) thread you will see that I have used this relation as evidence of a scientific consensus MIR (Mind Independent Reality) element (before it becomes part of the scientific consensus MDR) several times. http://forum.cosmoquest.org/showthre...-about-reality.
    OK, what I was hoping for was more along the lines of "and here is a published scientific reason why the two might be related, even if it is only speculative". Not a reference to your own personal use of it in a debate about philosophy.

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    This blog entry by Stacy McGaugh captures what a lot of astronomers are saying about that paper. TL;DR - surface-brightness limitations mean that the parts of galaxies now observable at these redshifts are too small to make the claimed conclusions, and we already know statistical things about disk galaxies at that redshift which indicate that more complex modeling is needed to support the dark-matter claims in the paper.

    (Note for bystanders - the journal Nature does have a track record of preferring to publish papers that will be talked about over those that are less flashy but longer-lasting. Not being pejorative, that's their stated policy. In astronomy, despite having published there a few times, I agree that Nature papers get an extra grain of salt from all my colleagues).

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