All Questions
73
questions
0
votes
1
answer
50
views
Limiting the mass of the neutrino for a relativistic case
I came across a question that states
What mass would a neutrino need to still be relativistic today (T = 2.37K) ?
So for a particle to be relativistic we need $pc \gg mc^2$
Well Neutrino was ...
- 3,122
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
0
votes
1
answer
92
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Sterile neutrinos findings
There is a relatively new paper https://arxiv.org/abs/1805.12028 of MiniBooNE on measurements of neutrino oscillations that can only be explained by the postulate of a sterile neutrino. I also read ...
- 9,778
2
votes
2
answers
309
views
How do you distinguish between missing momentum from a neutrino and from dark matter?
I thought googling this would give me an answer quite quickly, but actually couldn't find much, so maybe it's a silly question. But I read that dark matter searches rely on measuring missing momentum ...
- 979
7
votes
1
answer
826
views
Neutrino energy density vs photon energy density
So I'm currently following a course in Cosmology and we're covering the densities of different species in the universe right now. Starting from the photon density $\rho_{\gamma}$ we need to derive the ...
- 548
2
votes
1
answer
47
views
Lack of knowledge about ambient neutrinos below a certain energy?
A colleague and I were discussing the fact that beta decay can emit neutrinos with arbitrarily low energies. We have neutrino detectors that can detect solar neutrinos -- and maybe extrasolar ...
user4552
3
votes
1
answer
107
views
Is there a bound on the number of sterile neutrinos from cosmological observations?
The right-handed sterile neutrinos $\nu_{R}$ are electroweak singlets. They do not contribute to the electroweak anomaly, and therefore, their number is not fixed by the requirement of the anomaly ...
- 26.8k
11
votes
2
answers
547
views
If neutrinos are disfavoured as DM candidates why aren't axions?
Numerical simulations of observed large-scale structure formation work best with Cold Dark Matter (CDM; see the answer here). Neutrinos are candidates for Hot Dark Matter (HDM), and hence they cannot ...
- 26.8k
0
votes
1
answer
210
views
Estimate of neutrino masses from the values of $\Delta m_{21}^2$ and $\Delta m_{13}^2$ only!
The blog here says that
The measured mass differences between the eigenstates are $\Delta m_{21}^2=7.5\times 10^{-5} {\rm eV}^2$ and $\Delta m_{13}^2=2.5\times 10^{-3} {\rm eV}^2$, suggesting that ...
- 26.8k
0
votes
1
answer
303
views
Energy density, pressure and temperature for massive neutrinos in cosmology
I want to be able to numerically compute the mean energy density and pressure for a massive neutrino species in cosmology, at any given scale factor $a$. These are given in terms of the distribution ...
- 121
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
3
votes
1
answer
234
views
Why are there no more galaxies moving as relativistic speeds?
Introductory note: I am not discussing galaxies that are going away from us or that are at the border of the universe.
If there are no preferred frames of reference, no galaxy or matter ensemble can ...
- 5,568
4
votes
2
answers
812
views
How do we know that the dark matter is cold or non-relativistic? [duplicate]
According to the $\Lambda$CDM parametrization of the Standard Model of Big Bang cosmology, the universe contains a cosmological constant $\Lambda$ associated with $73\%$ dark energy, $23\%$cold dark ...
- 26.8k
3
votes
1
answer
145
views
Neutrino massless species
We do know that at least two neutrino species are massive. But, as far as I know, one neutrino species could be massless. How to determine if ONE of the current neutrino species (e.g., electron ...
- 6,611
4
votes
1
answer
506
views
Cosmic gravitational background and its temperature [duplicate]
There is a cosmic microwave background, according to the Big Bang theory. There is also a cosmic neutrino background, at 1.945 K, yet to be discovered, according to the Big Bang theory. My question is:...
- 6,611