RE: Freezing-in and freezing-out dark matter
Your two posts are really inspiring, thanks for sharing your knowledge on this fascinating subject with the community!
The two hypothesis are quite attractive. However, I am wondering about the x axis… What is m/T ? I suppose it is related to time in some way. So when would the transitions occur (2 for the freeze out, 1 for the freeze in)?
Another more in depth question:
In your opinion, what factor(s) could decide which of the two scenarios should be favored? I suppose that the dark matter genesis would occurre at the same time as the genesis of quarks and gluon, condensing from the huge PE of the inflaton field, once the inflation had stopped.
(ll the inflaton field KE had been converted to PE during the inflation phase, leading to energy condensation into particles when the inflation stopped. If I remember well, I think this is called the re-ionization phase , although I find this term confusing… )
Within this model, the origin of the x axis would be around t = 10^-32 seconds. In conclusion, what would decide if the initial quantities of dark matter were small or not vs. standard matter and antimatter particles.
And finally, do we have an idea of the energies required to reach conditions for dark matter genesis? Will it ever be within our reach?
Lots of questions here, sorry, but it’s really a fascinating topic. :-)
I cannot answer everything there... But I will try. Let's further discuss :)
This is the dark matter mass over temperature. As the temperature of the universe decreases with time, this is give or take the time, but the conversion is not immediate. However, as the temperature at the time of the big bang is finite, this defines the origins of the x-axis.
The only way to know would (I think) be to observe dark matter and study its properties. Knowing its mass and how it interacts with the Standard Model will be helpful. As long as this is not realized, I am afraid no one can tell. Both scenarios are equally plausible. I recall that the main difference between them is that in the freeze-out case, dark matter is in thermal equilibrium with the quark and gluon plasma, where in the freeze-in case, it is decoupled.
I am not too sure to see how the reionization plays a role here, but I may not have got the question correctly. And I am also not too sure about what you mean by quark, gluon and dark matter genesis? Sorry... Here we need to discuss more, I guess :)
Well , I understood that particles were created during the re-ionization phase (just as the Inflation ceased): Some of the potential energy of the inflaton field was converted to particles (Basically quarks and gluons). This is what I mean by quark and gluon genesis.
I was wondering if dark matter could have been created in the same process, or if it would have been the decay of the heaviest quarks + energetic collisions of quarks that could have created it, or a combination of both.
And in the end, if calculations based on the various inflaton field models could predict which of the freeze-out or freeze-in model would be favored (i.e., determining the relative quantity of Dark Matter created vs. normal matter).
Of course, these questions are only valid if we assume the inflationary models to hold some truth...
I guess that this is a very model dependent question and depending on the theory, you could have one or the other. For instance, in freeze-in model, there is no dark matter in the early days and it appears progressively. In freeze-out model, it could (should) be connected to inflation somehow.
Some could probably, I would say. But this is not easy (as one would try to solve many questions simultaneously).