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B Dark matter variations on Earth

  1. Nov 16, 2017 #51

    mfb

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    By definition, yes (WI in WIMP). That doesn’t mean dark matter has to consist of WIMPs.
    Additional particles don’t have to participate in the weak interaction, it is just likely.
    Null results of detectors looking for weak interactions are perfectly consistent with particles with no weak interaction.
     
  2. Nov 16, 2017 #52

    ohwilleke

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    Particles with no weak, strong or EM interactions are not only perfectly consistent with the non-detection of dark matter in direct detection experiments and the non-detection of DM at the LHC. They are also consistent with the absence of any compelling DM annihilation signature. So, while non-detection of DM in those channels is parameter bounding for DM theories, it certainly doesn't rule out DM that is "sterile" (i.e. that only interacts via gravity) or DM that only interacts with other DM in addition to gravity.

    The trouble is that the amount of correlation between inferred DM distributions and baryonic matter distributions is too tight to be explained by gravity alone and the shape of the DM distributions aren't what we would theoretically predict if DM was truly sterile or only interacted with other DM. So, truly sterile DM or DM that only interacts with other DM isn't enough to explain the phenomenology.

    This leaves you looking for a fifth force that predominantly governs DM-ordinary matter interactions (and possibly also DM to DM interactions), such as the paper described below, in a dark matter particle theory.

    Andres Olivares-Del Campo, et al., "Dark matter-neutrino interactions through the lens of their cosmological implications" (November 14 2017).
     
  3. Nov 17, 2017 #53
    May I know what this "correlation" you were referring to that indicates the amount of correlation between inferred DM distributions and baryonic matter distributions is too tight to be explained by gravity alone? Some references directly about it perhaps? Thank you

     
  4. Nov 17, 2017 #54
    It says it solves some problems for CDM also it can simulate on large scales.

    But in general it doesnt seem to me a perfect candidate to understand the general description of CDM. As ohwilleke pointed out we need a new model and maybe even a new force.
     
    Last edited: Nov 17, 2017
  5. Nov 18, 2017 #55

    ohwilleke

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    Some references can be found in thIs post. I don't specifically mention it there but collisionless bosonic dark matter models also don't work.
     
  6. Feb 5, 2018 #56
    Just for sake of understanding of your "fifth force that predominantly governs DM-ordinary matter interactions (and possibly also DM to DM interactions)", supposed you had a dark matter jacket that somehow got binded to your body and the dark matter jacket weights 50 lbs and you weight 100 lbs.. what would happen if you put yourself in a weighting scale. Would it register 150 pounds or 100 pounds? I know the dark matter jacket won't affect the weighing scale directly and it won't be pull down because the earth won't attract it.. so I guess it can just cause a drag in your body when you run.. can this drag be measured? In cosmological setting.. what are the results of attempts to measure this drag?
     
    Last edited: Feb 5, 2018
  7. Feb 5, 2018 #57

    Drakkith

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    It would certainly be attracted to the Earth, as dark matter interacts gravitationally with normal matter. If you could somehow attach this jacket to yourself you would find that you weighed more. There would be no drag though, as that requires an EM interaction, which dark matter doesn't have.
     
  8. Feb 5, 2018 #58
    Hmm... don't they make weighing scale in the labs that can measure the dark matter flux by coupling using the fifth force with dark matter moving all around.. it should register different readings.. shouldn't it?
     
  9. Feb 5, 2018 #59
    Are there dark matter candidates which don't contain mass but only pure energy (which can still interact with gravity)?

    If a particle has no mass (like photons) it moves at the speed of light... but photons have energy... I mean.. if dark matter contains no mass but only energy.. should it move at speed of light too?
     
  10. Feb 6, 2018 #60

    ohwilleke

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    A massless particle moves at the speed of light which is inconsistent with dark matter which has sub-relativistic speeds (i.e. it is 'warm" or "cold" dark matter, not "hot" dark matter) if it exists in the form of a particle, although massless particles could, in principle be confined in a massive composite particle (e.g. a "glueball"). For the same reason, ordinary neutrinos cannot be dark matter because they are too "hot" which is to say that their average velocity is too large.
     
  11. Feb 6, 2018 #61
    what dark matter candidates are like glueball where the massless dark matter particles could be confined in the massive composite particle as you described?
     
  12. Feb 6, 2018 #62

    mfb

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    I have no idea what you are talking about, but the answer is no. Nothing that would fit to your description is done.
     
  13. Feb 6, 2018 #63
    That are the constraints data on the general estimate of dark enough volume in the entire solar system besides that it has mass equivalent of a modest sized asteroid.. like could it have 10 times the volume of a modest size asteroid and still consistent with the data?

    What is the maximum volume or threshold (compared to this reference modest size asteroid) when they can already affect the orbits of the planets?
     
  14. Feb 7, 2018 #64

    mfb

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    Can you rephrase this question?
    Dark matter doesn't have a volume. If you multiply the volume of the solar system (defined by the outermost planet, the Kuiper belt, the transition to the interstellar medium or whatever you like) and multiply it by the local dark matter density you get this asteroid-scale mass value.

    To calculate the influence of dark matter on an orbit, only dark matter closer to the Sun is relevant, so the volume is fixed by the object you consider.
     
  15. Feb 7, 2018 #65
    typo, the "t" should be "w" or "what".

    I meant, local dark matter density can vary between between regions in the cosmos, correct? So how many multiples increase in the local dark matter density of our solar system before it can change the gravitational properties of our solar system?

    And if dark matter in our solar system is only asteroid-scale mass value.. how come it is said there are more dark matter than matter in the universe.. maybe you mean there are more dark matter in the outer region of galaxies and they are all crowding there?

    ohwilleke mentioned about fifth force that predominantly governed DM-ordinary matter interactions (and possibly also DM to DM interactions)? So why is this not accepted as solution?


     
  16. Feb 7, 2018 #66

    phinds

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    Uh ... because there IS?
    Yes, the distribution of dark matter is not based on solar systems, it is spread somewhat evenly throughout the galaxy and the total volume of the galaxy makes the volume of our solar system approximately zero, thus the low absolute amount of DM in our solar system.

    What's also true is that apparently the density of DM in our solar system IS anomalously low compared to the galaxy as a whole but I don't recall by what factor.

    What "5th force"?
     
  17. Feb 7, 2018 #67
    How do we know that the density of DM in our solar system is anomalously low? If there is an increased of 100 times or say the dark matter from other part of the galaxy travels to ours because they can become dynamic due to some 5th force complexities or interactions.. can we measure it?

    you missed ohwilleke post #52 where he shared:

    "This leaves you looking for a fifth force that predominantly governs DM-ordinary matter interactions (and possibly also DM to DM interactions), such as the paper described below, in a dark matter particle theory.

    Andres Olivares-Del Campo, et al., "Dark matter-neutrino interactions through the lens of their cosmological implications" (November 14 2017)."
     
  18. Feb 7, 2018 #68

    phinds

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    Good question. I don't recall. I just recall reading somewhere here on PF that that is the case.
    As far as I am aware that kind of change in the DM density just doesn't happen.

    Oh, yeah. I forgot about that because I considered it speculative (I could be wrong)
     
  19. Feb 7, 2018 #69

    mfb

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    It does.
    Many orders of magnitude. Sure, people searched for it, but without expecting and without finding any effect.
    Our solar system is not a typical place in our galaxy - it is a lot of mass in a small volume. Take a cubic light year containing our solar system and you get 1/4 Jupiter mass as dark matter. Take 5000 cubic light years and you get the mass of the solar system.
    It is not.
    There is absolutely no indication of any fifth interaction, why do you keep bringing this up?
     
  20. Feb 7, 2018 #70

    phinds

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    Hm ... I was SURE that I had read here on PF that it is, and that that was backed up by published information (although I have no recollection of the provenance of same). I'll poke around and see if I can find something. Perhaps I misunderstood.

    EDIT: well, I'm coming up w/ nothing. Senior moment maybe.

    2nd EDIT: I did find a pop-sci article that does at least support my recollection of having read about lower than expected DM in the solar system:

    https://www.forbes.com/sites/alexkn...detect-dark-matter-near-the-sun/#1920ca287e0e

    a quote from it:

     
    Last edited: Feb 7, 2018
  21. Feb 7, 2018 #71

    phinds

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    I do not consider this source to be authoritative, however you might be interested in the article:
    https://darkmatterdarkenergy.com/2013/08/30/dark-matter-in-the-solar-system-does-it-matter/

    A quote from it:
     
  22. Feb 7, 2018 #72

    ohwilleke

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    The density of DM in the solar system hasn't been measured directly and is not assumed to be anomalously low. The density of DM in the galaxy is low everywhere. But, most of the galaxy is empty space. The lion's share of the volume of the galaxy isn't in any star system and the inferred dimensions of the DM halo extend far above and far below the galactic plane where there is also almost nothing. But, because gravity is cumulative, all of the very thin DM density in places where there aren't star systems adds up to a lot of gravitational effect.

    And, even if DM were far more than the inferred amount of DM in the solar system based upon the solar system density (which is about the mass of an asteroid all together), for example, even if the actual amount DM in the solar system had the mass of the planet Neptune in the aggregate, we probably still couldn't detect it, because DM, by definition, is distributed more or less uniformly and doesn't clump. So, a 0.1% increase or so in the total mass of the solar system evenly spread throughout the solar system would be very hard to distinguish from a no DM scenario based upon dynamics.
     
  23. Feb 7, 2018 #73

    ohwilleke

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    Not true. The evidence is that completely collisionless DM is inconsistent with the observed distribution of DM. Therefore, there has to be either self-interaction in DM or a baryonic-DM interaction or modified gravity. See, e.g.:

    * Paolo Salucci and Nicola Turini, "Evidences for Collisional Dark Matter In Galaxies?" (July 4, 2017). Abstract:
    * Dark matter distributions have to closely track baryon distributions, even though there is no viable mechanism to do so: Edo van Uitert, et al., "Halo ellipticity of GAMA galaxy groups from KiDS weak lensing" (October 13, 2016).
     
  24. Feb 7, 2018 #74
    Is it possible the dark matter are neither WIMPS, Axions, heavy sterile neutrinos, low-mass black holes nor particles that interact via new fundamental forces and dark matter “atoms” that include dark correlates of protons, neutrons and electrons but is composed of altogether new field or dark matter field consisting of information field that guides, maintain, supervises, etc. the visible baryonic matter and evolution of the cosmos? This makes a lot of sense than the former group of candidates. Would you happen to have papers that explored what I just described?
     
  25. Feb 7, 2018 #75

    Vanadium 50

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    So far so good..

    So far so good...

    No. This is just woo.
     
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