All Questions
73
questions
2
votes
0
answers
80
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....
- 2,466
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 ...
- 2,466
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
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
3
votes
1
answer
84
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
0
votes
0
answers
31
views
Why can't Dark matter be made up mostly of Neutrinos? [duplicate]
It's said that Neutirnos can only make up a tiny fraciton of dark matter.
So why can't Dark matter be mostly made up of Neutrinos?
Why can't there just be a huge number of them?
I suspect myself that ...
- 2,888
3
votes
2
answers
413
views
How does neutrino free streaming length affect the growth of structures in the universe?
I cannot quite wrap my head around the exact mechanism by which neutrinos affect cosmic structure growth. Their effect as dark matter is clear to me but I don't understand how their longer free ...
- 280
4
votes
2
answers
125
views
Experimental distinction between neutrinos and antineutrinos
How can we experimentally distinguish left-handed neutrinos from right-handed antineutrinos when we do not know a priori their creation process (for example in the case of cosmological neutrinos)?
- 51
2
votes
1
answer
121
views
Dark energy and neutrinos
Neutrinos are sometimes considered to contribute to dark matter, see e.g. E.Siegel.
Why not for dark energy?
There is a similar scale in energy density involved. If you use the current upper limit for ...
- 95
4
votes
1
answer
476
views
Cosmic neutrino background temperature
In my cosmology lecture course, we derived the temperature of the cosmic neutrino background as
\begin{equation}
T_{\nu} = \left(\frac{4}{11}\right) ^ {1/3} T_{\gamma} \,.
\end{equation}
Since the ...
- 109
3
votes
4
answers
419
views
How can the Cosmic Neutrino Background (CνB) have a temperature? How can any neutrino have a 'temperature'?
The word temperature usually refers to the average velocity of massive particles, correct?
And the Cosmic Microwave Background (CMB) has a 'temperature' based on the temperature of a 'black body' that ...
- 4,515
3
votes
1
answer
75
views
How did neutrinos eliminated from dark matter? [duplicate]
I am reading "Dark Matter and Dark Energy" by Brian Clegg.
In Chapter 3 it's discussing about cosmic microwave background radiation and the elliptical shape
of early universe obtained from ...
0
votes
1
answer
489
views
What is the 'effective number of neutrino species'? And how does that, rather than the total number of them, affect the universe?
As stated above...
How can the the physics of early cosmology (articles about which are where I usually come across mentions of such) be affected by an 'effective' number of neutrino types, rather ...
- 4,515
0
votes
1
answer
32
views
Energy density of a neutrino species
My question refers to the derivation of the energy density $p_{\nu,i}$ of a neutrino species given in the footnote on page 16 of Lecture Notes on Cosmology by Komatsu. I have reproduced this below:
$$...
- 201
0
votes
1
answer
77
views
Neutrino temperature
I was wondering if anybody knows the relation between the photon temperature $T$ and neutrino temperature $T_{\nu}$? And why this can be written as
$$T_{\nu}=\left(\frac{4}{11}\right)^{1 / 3} T \...
- 1