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Dark Matter Temperture

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#1 Kkalahiki20

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Posted 25 November 2019 - 02:37 PM

Hey guys does anyone know what the temperature of dark matter is? Wether it being cold, warm, no temperature, or both?



#2 sg6

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Posted 25 November 2019 - 02:54 PM

Never actually heard of one and I also have the idea that Hot, Warm or Cold Dark matter relates more to the mass of a single piece of it, and so the speed that it may move.

 

Hot Dark matter being the neutrino mass stuff, if there is any. Cold Dark Matter being the simple big heavy stuff and the Warm Dark Matter being an intermediate to answer other ideas/theories/aspects/discrepancies.

 

So a little unsure if it actually relates to a "temperature".


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#3 kathyastro

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Posted 25 November 2019 - 02:59 PM

I'd think they need to have an idea what it is before they can determine a temperature.


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#4 rehling

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Posted 25 November 2019 - 03:04 PM

We don't know enough about it to know if it has a temperature. Temperature relates to the vibratory energy in molecules, and for some (most? all?) of the candidate explanations, there would be no equivalent. On the other hand, no explanation has been borne out, and some have been refuted, so there's no way to answer now.


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#5 sg6

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Posted 25 November 2019 - 03:26 PM

Apparently besides Hot, Warm and Cold we have Fuzzy DM as well. confused1.gif

 

Fuzzy-DM



#6 SteveG

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Posted 26 November 2019 - 03:55 PM

It may turn out to be a new force of nature, so no temperature at all.



#7 Bob Abraham

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Posted 27 November 2019 - 11:17 PM

When people refer to temperature in this context, they refer to temperature in the sense of the mean kinetic energy of the particle.

 

Much of the lexicon of dark matter was set in place by people using dark matter models to try to explain the distribution of the large scale structure of galaxies. Hot dark matter particles (such as neutrinos with masses of a few eV) move quickly and they can smooth out small-scale structures. Cold dark matter particles move more slowly, so the small-scale structure (imprinted at the time of the early Universe) leaves a detectable imprint. Thus in cold dark matter models you have a lot of small-scale structure in the distribution of galaxies, while in hot dark matter models you do not.

 

Fuzzy dark matter is conceptually rather different... and amazingly interesting. Fuzzy dark matter postulates that dark matter is made of ultra-light particles that move so fast they display quantum mechanical behavior on cosmological scales. The 'fuzziness' referred to in the name is in the sense of the Heisenberg uncertainty principle limiting your information. This class of models is turning out to be quite testable, because it predicts (for example) that if you can find galaxies that are very dark matter dominated in their cores they will exhibit spikes in their velocity dispersion measurements near their very centers. People have started looking for these, but the observations are very challenging even with the largest telescopes. So far nobody has found one of the 'soliton cores' that are the signature of fuzzy dark matter, but it is early days for this kind of work.




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