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It has been argued that structure on subgalactic scales is incompatible with standard ideas about cold dark matter, and that instead it indicates "warm dark matter" made of particles with a mass of about 1 keV. At the same time, there are possible observations of dark matter accumulating at scales of 10 GeV and >100 GeV, which is more in the usual range ...

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No, it is not a crazy effort. And no, dark matter absorbed by the underground experiments – many of them actually claim some evidence of such a new particle, see yesterday's update http://motls.blogspot.cz/2013/06/hooper-xenon100-may-see-dm-candidates.html?m=1 isn't far away. Dark matter penetrates every corner of every galaxy and it actually fills a ...

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In an FRW cosmology, we have a scale factor $a$. For example, if $a$ grows by a factor of 2, galaxies have gotten twice as far away as before. The contribution to the stress-energy tensor from radiation goes like $a^{-4}$, from massive particles $a^{-3}$, and from a cosmological constant $a^0$, i.e., it's constant. For these reasons, the universe has gone ...

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