All Questions
6
questions
1
vote
0
answers
37
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Axions approaching thermal distribution
I am reading Sikivie's paper on Axion Cosmology. I have the equation:
$$\frac{\mathrm{d}}{\mathrm{dt}}[R^3(n_a^{th}-n_a^{eq})] = -\Gamma R^3(n_a^{th}-n_a^{eq}) \tag{1}$$
where $R(t)$ is the ...
- 1,222
15
votes
4
answers
3k
views
If dark matter can't lose kinetic energy, then why is it not traveling at relativistic speeds?
I have read this question:
The only way you can do this is to remove kinetic energy from the system.
With normal matter this is done through electromagnetic interactions, which turn the kinetic ...
- 29k
1
vote
1
answer
53
views
Number of interaction of early universe
I am reading An introduction to particle dark matter by Stefano Profumo. I am struggling on a derivation.
As given from the text, in the early universe $\frac{\dot{T}}{T}=-\frac{\dot{a}}{a}=-H$, ...
- 567
0
votes
1
answer
218
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Chemical equilibrium for a $2-2$ scattering and Boltzmann equation in cosmology and astroparticle physics
Definition of chemical equilibrium According to the definition of chemical equilibrium in Wikipedia, it is a situation where the rate of the forward reaction is same as the rate of backward reaction ...
- 26.8k
1
vote
0
answers
32
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What might be the equillibrium Distribution Function of Dark Matter?
Can we assign a thermal distribution function to Dark Matter(not necessarily known ones)?
Is it possible that they won't even follow thermal distribution function and maybe a function of something ...
- 624
12
votes
1
answer
748
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Integrated Boltzmann equation for dark matter
In Dodelson's book, the equation for a scattering process $ a + b \Leftrightarrow c + d $ is given as
\begin{align}
a^{-3} \frac{\mathrm d (n_a a^3)}{\mathrm d t}&=-n^{\text{eq}}_a n^{\text{eq}}...
- 301