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Interesting article about dark matter

  1. Mar 4, 2015 #1
    Last edited: Mar 5, 2015
  2. jcsd
  3. Mar 4, 2015 #2

    Simon Bridge

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    In physics, something is "black" if it absorbs lots of the light that hits it - an ideal "black body" for instance absorbs all the light that hits it.
    Being black, in this sense, does not stop something from also glowing,

    For an object to be black in color, it need only absorb light in the visible spectrum.

    Dark Matter (DM) by comparison, does not interact with light at all, light just passes right through, and it is a label to be used until we can figure out what is going on.
    The article is about this sort of DM and how it may be interacting with the regular matter in Neutron stars to result in the statistical lack of neutron stars in the galactic core.
    It goes on to tell you what sort of stuff this sort of DM would be consistent with. If the theory is right, and that's a big "if", then it narrows down the field of possibilities.

    DM is unlikely to explain where all the regular antimatter ended up - why would anti-DM gravitating to anti-matter do anything special?
    More likely a similar mechanism gave rise to the asymmetry of both types of matter.

    The article is very speculative right now - it is not even clear how you'd be able to tell if a pulsar were dying due to dark matter or not and there are other possibilities for the lack of pulsars in the galactic core.
     
  4. Mar 4, 2015 #3

    Drakkith

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    The article doesn't propose any new type of dark matter. It only proposes that enough of it may be 'accumulating' in a neutron star to cause to to turn into a black hole.

    I suppose it's possible, but at this time it doesn't help us much as far as I know.
     
  5. Mar 5, 2015 #4
    Simon, I meant dark. I seem to have written black instead of dark. Very strange.

    The anti matter very long shot idea was just a brainstorming suggestion to solve two mysteries with "one stone"..
     
  6. Mar 5, 2015 #5

    Chronos

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    Tanelorn, you obviously are smart enough to realize this is a bunch of bull, so why parade it here?
     
  7. Mar 5, 2015 #6

    Garth

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    Or at least give references to published papers or physics ArXiv eprints.

    Garth
     
  8. Mar 5, 2015 #7
    Sorry guys, it was a just spur of the moment, ASIDE QUESTION.
    I only know that we have two mysteries and I just wondered if there was any connection there:

    1. Where did all the anti-matter go?
    2. What is dark matter made of and where did it come from? - and 5 times more DM mass than normal matter at that.

    I am certainly not clever enough to know that there was DEFINATELY no connection.
     
    Last edited: Mar 5, 2015
  9. Mar 5, 2015 #8

    Drakkith

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    I didn't have a problem with your post.
     
  10. Mar 5, 2015 #9

    PeterDonis

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    That isn't a mystery; it all got annihilated by matter as the early universe expanded and cooled. The mystery is why there was a small amount of matter left over; ordinarily we would expect matter and antimatter to be created in equal quantities at the end of the inflation era, so the annihilation process would have left only radiation behind. However, the discovery of CP violations in the weak interaction provided a mechanism that could produced a slight asymmetry between matter and antimatter; this is currently believed to be the reason why our universe today contains matter but (practically) no antimatter.
     
  11. Mar 5, 2015 #10
    Thanks Peter, I am pretty sure I did know this, but apparently not yesterday.
     
    Last edited: Mar 5, 2015
  12. Mar 7, 2015 #11
    Is there a lack neutron stars in globular clusters as well?
     
  13. Mar 23, 2015 #12
    As I understand the observable gravitational effects of dark matter, the speculation introduced in the referenced article ignores much about these observations. I am sorry I cannot readily cite a source reference, but a major part of the dark matter in the universe is all around and through galactic clusters, not just in the galaxies. The behavior of the motion of galaxies in clusters requires this to be so.
     
  14. Mar 24, 2015 #13

    Chronos

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  15. Dec 12, 2015 #14
    Hi @Simon Bridge and @Drakkith:

    What I find puzzling about this idea is that there is an implication that there is a much higher concentration of DM near the galaxy core than the average in the halo. From recent dialogs in other threads, I have come to understand that in order for a DM particle to change its orbit relative to a central mass from one of large geometry to smaller, it has to get rid of its energy. Also, unlike baryonic matter, this is very unlikely since DM doesn't have interactions that can create photons to radiate away the orbital energy, as happens with baryonic matter.

    Regards,
    Buzz
     
  16. Dec 12, 2015 #15
    I think the answer to this could be that not all orbits are perfectly circular. in fact that would probably be rare.
    An eliptical orbit can have the orbiting object sometimes closer and sometimes further from the COM without needing to lose energy.
    It only has to travel faster when nearer to the COM, and only gravity is involved.
     
    Last edited: Dec 12, 2015
  17. Dec 12, 2015 #16
    Hi rootone:

    The problem with a DM particle P in large elliptical orbit falling onto a neutron star (NS) is that P will have to hit the surface of NS, and that is a very tiny target. Also, the angle at which P hits NS may have further limiting constraints. AFAIK, no one has done any analysis about this possibility, calculating the fraction of the DM halo that might hit and be captured by the NS, that is, not just pass through a portion of the NS and continue its orbit.

    Regards,
    Buzz
     
  18. Dec 12, 2015 #17

    Simon Bridge

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    Maths for the capture of Dark Matter by Neutron stars has been done.
    http://arxiv.org/abs/1201.2400
    ... I find many hits for this and other papers in a casual search.
     
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