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What is the temperature of cold & hot dark matter?

  1. Jun 24, 2011 #1
    what is the temperature of cold & hot dark matter?
  2. jcsd
  3. Jun 24, 2011 #2
    Neither has a well-defined temperature.
    The terms 'hot' and 'cold' refer to characteristics of the dark matter, and how they behave---namely, hot dark-matter would be highly-relativistic (and in the past, was believed to be more strongly interacting); while cold dark matter is non-relativistic (and incredibly weakly interacting).

    'Temperature' is only well defined in a collisionally dominated ensemble of particles that are well described by certain statistical distributions. It doesn't really make sense to say what the temperature of a single particle (for instance) is.
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