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Thread: Axions etc?

  1. #1
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    Axions etc?

    Sorry for another DM thread.

    Is it me or is there a change in the tone of words used when describing DM experiments?

    I used to be, "the experiment hopes to find...."

    These days it is more common to aim to "exclude energy ranges."
    ADMX has already eliminated the one of the two axion benchmark models from 1.9 μeV to 3.53 μeV, assuming axions saturate the Milky Way's halo
    Similarly measurements of Fine structure constant killing off dark photons was denounced as a positive result.

    To me any result is knowledge and therefore good, but is this part of a wider change in how scientists view DM?
    See: 'The God Kit' -- 'The Brigadier And The Pit' -- Carl N Graham -- Sci-fi blog: The Alien Reporter

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    Maybe a change in how it is reported? As writers realise that the "low hanging fruit" don't exist they have to take a more conservative approach to describing the work?

    It seems a natural change from not having any results and saying what you hope might happen, to having "negative" results and explaining how they narrow the search space.

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    Also a factor of the maturity of the theories. The theoretical framework for a lot of DM models has solidified and now rather than assumption filled direct tests there is more scope for these more indirect probes of the phase space for the theory.

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    It does seem the theoretical framework is still being pushed by along by experimental results.
    Not that that is bad in anyway.

    When asking for funding for an experiment to search for DM, the proposed detector now has be sensitive enough to provide a useful negative result.
    Is this pushing up the costs for future DM detectors?

    Can indirect probes ever give a definitive result?
    I am thinking we could reach a point where costs ends the search for DM.

    Maybe DM only interacts by gravity, what then?
    Can there be an experiment that proves a theory?

    Also, the amount of normal matter being found (missing or not) does not seem to be slowing down in the slightest. The harder we look the more we see, still seems to be true.
    If the trend continues could it have an impact on the DM search?
    See: 'The God Kit' -- 'The Brigadier And The Pit' -- Carl N Graham -- Sci-fi blog: The Alien Reporter

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    We nearly hit the point where costs stopped the hunt for the Higgs, it is quite possible the return on DM experiments will end up so low we need theory to catch up. But I'm fairly optimistic that enough people thinking hard thoughts about it will lead to better experiments or at least more testable ones. Part of the reason for the costs now is how close we insist on pushing the apparatus to the state of the art.

    Not sure what you mean by us seeing more matter, the inferred proportion of baryonic to non-baryonic hasn't shifted much.

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    Quote Originally Posted by Shaula View Post
    Not sure what you mean by us seeing more matter, the inferred proportion of baryonic to non-baryonic hasn't shifted much.
    A few weeks ago I was looking at stuff on intergalactic material, I did not remember the numbers being so big.
    The estimates on numbers of dim stars & remnants seem to have shot up.
    Also, the number of bright detectable stars now seems much higher than models of messy galactic interactions/mergers predicted.
    ....

    Then there are estimates of the mass of interstellar comets/asteroids population (based on a sample size of 1)
    Neutron star, black hole population estimates assuming asymmetric type II explosions send them into extreme orbits spending most of their time outside the visible galaxy.
    Better star mass numbers from watching exoplantes orbits.
    Just lots of little items that all add (brown dwarf systems etc)
    See: 'The God Kit' -- 'The Brigadier And The Pit' -- Carl N Graham -- Sci-fi blog: The Alien Reporter

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    Quote Originally Posted by PetTastic View Post
    A few weeks ago I was looking at stuff on intergalactic material, I did not remember the numbers being so big.
    The estimates on numbers of dim stars & remnants seem to have shot up.
    Also, the number of bright detectable stars now seems much higher than models of messy galactic interactions/mergers predicted.
    ....

    Then there are estimates of the mass of interstellar comets/asteroids population (based on a sample size of 1)
    Neutron star, black hole population estimates assuming asymmetric type II explosions send them into extreme orbits spending most of their time outside the visible galaxy.
    Better star mass numbers from watching exoplantes orbits.
    Just lots of little items that all add (brown dwarf systems etc)
    This is all matter we knew existed. It is just better characterised. The amount of matter estimated has remained quite steady for a long time and nothing short of ludicrous amounts of matter turning up is going to make a dent on the inferred ratios.

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    Quote Originally Posted by PetTastic View Post
    A few weeks ago I was looking at stuff on intergalactic material, I did not remember the numbers being so big.
    The estimates on numbers of dim stars & remnants seem to have shot up.
    Also, the number of bright detectable stars now seems much higher than models of messy galactic interactions/mergers predicted.
    ....

    Then there are estimates of the mass of interstellar comets/asteroids population (based on a sample size of 1)
    Neutron star, black hole population estimates assuming asymmetric type II explosions send them into extreme orbits spending most of their time outside the visible galaxy.
    Better star mass numbers from watching exoplantes orbits.
    Just lots of little items that all add (brown dwarf systems etc)
    This is more applicable to the missing baryon problem. Before 2017, we had found about 70% of the visible matter that is predicted. A 2017 detection of hot intergalactic gas should fill in the gap. The other "little items" such as intergalactic stars will fill in whatever remains.

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    Quote Originally Posted by Reality Check View Post
    This is more applicable to the missing baryon problem. Before 2017, we had found about 70% of the visible matter that is predicted. A 2017 detection of hot intergalactic gas should fill in the gap. The other "little items" such as intergalactic stars will fill in whatever remains.
    Yes, I was very excited about that at the time, but was the missing baryons already included in the DM calculations?
    Or do we have to knock ~10% off the amount of DM we are looking for?
    The detected baryons in the ICM are getting close to the 95% of all known mark, and almost none of this matter was known about when DM theories were well established.
    See: 'The God Kit' -- 'The Brigadier And The Pit' -- Carl N Graham -- Sci-fi blog: The Alien Reporter

  10. #10
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    Can we please keep this thread about Axions as Dark Matter? There are plenty of existing threads about missing baryons, and plenty of threads about WIMPS, or primordial black holes as Dark Matter.
    Forming opinions as we speak

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    What to me looks like one of the problems with axions as DM is the processes used for detecting them also should produce them.
    The CERN Axion Solar Telescope is looking for axions from the Sun.
    If they could be produced in the Sun, then quasars, (magnetic)white dwarf stars, neutron stars would produce much more?
    See: 'The God Kit' -- 'The Brigadier And The Pit' -- Carl N Graham -- Sci-fi blog: The Alien Reporter

  12. #12
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    Quote Originally Posted by PetTastic View Post
    What to me looks like one of the problems with axions as DM is the processes used for detecting them also should produce them.
    The CERN Axion Solar Telescope is looking for axions from the Sun.
    If they could be produced in the Sun, then quasars, (magnetic)white dwarf stars, neutron stars would produce much more?
    Just like with neutrinos, the Sun is by far the brightest source of Axions (if they exist) as seen from the Earth.
    To me the problem with Axions as dark matter is that I don't see a way for them to be Cold Dark Matter, or even Warm Dark Matter. They have to travel at undetectably less than c, because they have so little mass, and so much energy. Most models of the universe these days allow a few percent of the mass being made of Hot Dark Matter (e.g. neutrinos). Perhaps Axions make up some of that.
    Forming opinions as we speak

  13. #13
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    I can't find much in the way of mechanisms for cooling Axions(if they exist).
    There seems to be hints of a selection mechanism, that hot or cold Axions maybe more more likely to turn into photons in some conditions, but I don't understand which way the bias goes.
    See: 'The God Kit' -- 'The Brigadier And The Pit' -- Carl N Graham -- Sci-fi blog: The Alien Reporter

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