All Questions
7
questions
3
votes
1
answer
132
views
Cosmological perturbations and energy in an expanding universe?
I was reading an interesting book from cosmomogist Viatcheslav Mukhanov Physical Foundations of Cosmology and I had a specific question about it:
It is usually said that energy conservation is ...
- 2,462
3
votes
2
answers
112
views
Can there be some kind of photon emission caused by cosmological expansion?
Are there any kind of observed and experimentally verified processes or mechanisms where photon emission occurs and which are directly cause by spacetime expansion in some way?
- 2,462
0
votes
0
answers
96
views
From a true vacuum to a false vacuum in expanding space?
It is known that spacetime expansion affects many aspects in the universe. For instance, due to this, a global definition of energy conservation is difficult to define.
Could this expansion affect the ...
- 2,462
0
votes
1
answer
493
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 ...
- 4,509
3
votes
1
answer
199
views
Why is the homogeneity problem actually a problem?
I don't mean to be flippant but I have never understood why the homogeneity in the universe needs.explaining. I have searched other questions on stack exchange and they don't really address the ...
- 1,087
1
vote
0
answers
23
views
Are atomic energies increasing as the Universe expands? [duplicate]
Starting from the FRW metric (for simplicity flat space, radial direction only):
$$ds^2=-c^2dt^2+a(t)^2dr^2$$
If we take $dt=0$ then the proper distance $ds(t)$ between two spatially separated ...
- 5,925
3
votes
4
answers
801
views
Exploring beyond event horizons
In the expanding universe the velocity of separation between galaxies depends upon how far they are. If they are much far away will they have relative velocity of separation greater than speed of ...
- 69