All Questions
28
questions
3
votes
2
answers
153
views
Does neglecting dark matter solve the Hubble tension?
If the total mass of the universe is smaller than estimated by neglecting the gravitational pull of dark matter, the estimated expansion rate should be greater.
Does this consideration in the CMB ...
- 476
0
votes
3
answers
108
views
Is Dark Energy Taking Over?
First question, trying to keep it simple 😃
Because it's constant it grows in magnitude as the universe expands, whereas normal matter does not? Is this accurate as far as we know?
- 11
1
vote
1
answer
60
views
Reference: 1+1D paper-model representation of the Lambda-CDM cosmological model
I'm looking for a 1+1D (1 time + 1 space dimension) paper model of the current $\Lambda$CDM cosmological model; if possible, one which somehow respects the scales of geodesic spacelike distances at ...
-3
votes
2
answers
267
views
Does anyone really know how dark energy/matter works?
If dark energy has no physical interaction with normal matter but it does interact with dark matter, wouldn't that cause an interaction with normal matter through its interaction with dark matter and ...
- 1
0
votes
1
answer
42
views
$Ω = ρ/ρ[c]$, so although near to 1, for an accelerating expansion $Ω$ must be below 1. What's its value?
$Ω$ is taken to have different components - ordinary matter, dark matter, dark energy. But because it is expressed in relation to the critical density for attractive gravity, it seems that omega is ...
- 85
1
vote
1
answer
35
views
Is there data regarding the large-scale density (mass/volume) of “dark matter plus ordinary matter,” as a function of time?
Here, large-scale means (conceptually) the known universe. Hopefully, the data runs from (perhaps somewhat after) the Big Bang until now. Pointers to such results would be appreciated.
15
votes
4
answers
3k
views
If dark matter can't lose kinetic energy, then why is it not traveling at relativistic speeds?
I have read this question:
The only way you can do this is to remove kinetic energy from the system.
With normal matter this is done through electromagnetic interactions, which turn the kinetic ...
- 29k
3
votes
1
answer
337
views
If dark matter can't clump together, then where was it when the observable universe was much smaller at the beginning of the universe?
I have read this question:
To zeroth order, dark matter can only 'clump' as much as its initial energy (obtained soon after the big-bang) allows. One example of such a 'clump' is a 'Dark Matter Halo' ...
- 29k
0
votes
3
answers
213
views
Is it possible that dark matter and dark energy come from the same dark particle?
I've skimmed articles/blogs and watched videos around this issue, and the universal consensus is that dark matter and dark energy are two different things >> DM is attractive while DE is ...
- 137
4
votes
1
answer
135
views
What does it mean for CDM to "decouple from baryons"
I am currently working on my Final Year Project as an undergraduate, mostly intended to be a review of $\Lambda$CDM model and some of its modern challenges.
When talking about Cold Dark Matter I ...
- 148
2
votes
1
answer
302
views
Friedmann equation and model universes
I was studying Barbara Ryden book on modern cosmology, on it's 5th chapter, she introduces the following image:
This image summarises the general behaviour of the Hubble constant. I was wondering, ...
- 97
14
votes
3
answers
2k
views
Why is dark energy dominant between galaxies but not inside galaxies?
The ideas of dark matter and dark energy are mind blowing.
Why is it said that dark matter overcomes dark energy in galaxies but it loses the battle in intergalactic space? In other words, why is dark ...
- 1,148
0
votes
2
answers
118
views
Dark matter and velocity [duplicate]
We know that as the speed of an object increases, so does its relativistic mass.
But can it be said that dark matter may be due to the increasing relativistic mass of nebulae, stars, galaxies, etc. ...
1
vote
2
answers
982
views
What is the mathematical expression of the Lambda-CDM model?
The conceptual meaning of this model is clear to me. But where can I find the actual mathematical model?
The Wikipedia page says "The simple ΛCDM model is based on six parameters". Six parameter ...
- 1,171
6
votes
2
answers
160
views
How do we know that dark matter energy density scales as $\rho\propto a^{-3}$?
How do we know that dark matter energy density scales as $\rho\propto a^{-3}$?
- 26.8k