All Questions
19
questions with no upvoted or accepted answers
13
votes
0
answers
382
views
Are there any experimental bounds on the ratio of neutrinos to antineutrinos in the universe?
In the Standard Model, both baryon number and lepton number are conserved quantities (excluding the theoretical possibility of sphaleron processes which are exceeding rare, at least at non-"near in ...
- 3,957
6
votes
0
answers
66
views
Sterile (4th) neutrino and cosmological bound
Recent results by MicroBoone seems to give support to old LSND experiment in favor of a fourth neutrino (sterile). How does it fit with the current cosmological bound for neutrinos?
- 6,611
4
votes
0
answers
182
views
How to understand particle decoupling in the early universe?
We often say that when the rate of some interactions, say the beta decay and electron capture, are slower that the rate of universe's expansion, then the corresponding particles, say neutrinos, ...
- 3,691
3
votes
1
answer
85
views
Will the universe be full of neutrinos?
If neutrinos are so easy to produce, but it rarely get absorbed or detected, doesn't that mean the universe will be full of neutrinos?
Will its density ever reach a balance where its absorption events ...
- 471
3
votes
0
answers
75
views
Active-sterile mixing for KeVins
People sometimes talk about KeV mass sterile neutrinos as a warm dark matter candidate. I think they call them KeVins (horrible name btw). Now, In order for it to be a good dark matter candidate it ...
- 1,043
2
votes
0
answers
90
views
Gravitational halos made of neutrinos...?
I have been recently interested in how halos made of standard model particles could be formed and behave.
After asking some questions in this site, I was told about how neutrinos could form such halos....
- 2,462
2
votes
0
answers
72
views
Why potential energy of a non-relativistic particle in an expanding universe is $ma^2\phi$?
I have been reading a paper on neutrino clustering in an expanding universe: see section 3, particularly 3.3.2 of this paper. In this paper for non-relativistic neutrinos, which travel through a ...
- 568
2
votes
0
answers
256
views
Using the boltzmann equation to find neutrino decoupling temperature
I'm an undergraduate student currently following a particle astrophysics lecture. I was reading some stuff about the neutrinos decoupling before the $e^+ e^-$ annihilations. It's possible to quickly ...
- 21
1
vote
0
answers
74
views
What mass do neutrinos have in the early universe?
Since neutrinos interact constantly in the early universe, I assume that they are present as flavor eigenstates. However, they are Fermi-Dirac distributed,
\begin{equation}
f(E, T) = \frac{1}{e^{E/T} +...
- 49
1
vote
0
answers
25
views
How do you relate the number densities of neutrinos and photons soon after the positron–electron annihilation?
I found this equation:
$n_\nu = \frac{3}{4} \frac{g_\nu T_\nu^3}{g_\gamma T_\gamma^3} n_\gamma$
Where does it come from?
- 84
1
vote
0
answers
45
views
Possibility of reaching equilibrium starting with a nonequilibrium initial condition in the early radiation-domination
Update after @knzhou's comment
If in a theory, the coupling of the dark matter (DM) field to the Standard Model (SM) fields is small enough, the rate of interaction of the DM particles in the ...
- 26.8k
1
vote
0
answers
57
views
$N$-body simulation with varying neutrino mass
I am trying to find a picture of the $N$-body simulations that shows the LSS. Particularly I am looking for different neutrino masses without the CDM. For instance pictures likes this
But with more ...
1
vote
0
answers
88
views
Deriving the free streaming distance for HDM particles
I am trying to derive the free-streaming length for the HDM particles but I couldnt follow the arguments given by the article https://arxiv.org/pdf/astro-ph/0201405v1.pdf after equation 83.
Thanks
- 3,122
0
votes
0
answers
53
views
Can there be structures made from neutrinos that can have angular momentum?
Would it be possible to eventually have structures made from neutrinos somewhere in the universe, as it is indicated in this question (Are neutrino stars theoretically possible?), like halos of ...
- 2,462
0
votes
0
answers
47
views
Neutrinos becoming mass eigenstates in the early universe
I have two points where I would need clarification:
Neutrinos are present in the early universe as flavor eigenstates and as such they decouple from the thermal bath, I guess. However, today, at ...
- 49