All Questions
10
questions
1
vote
1
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95
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Why do people say that the $\Lambda$-CDM model has six independent parameters?
The Wikipedia article on the $\Lambda$-CDM model says that the model has six "independent parameters". It also says that the model has several "fixed" parameters and several "...
- 48.4k
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 ...
-1
votes
1
answer
137
views
Could dark matter be just a gravitational effect of dark energy?
I'm wondering if we just looking at the two sides of the same coin and if there is actually a correlation of DM with DE?
Is it possible that DM just to be a gravitational effect (or an effect that ...
- 4,170
0
votes
1
answer
122
views
Could Dark Matter imply the existence of Dark energy? [closed]
This is admittedly a simple example, but it seems to check out. Consider the standard metric for the Schwarzschild solution in coordinates $(t, r,\theta,\phi)$:
$$ g_{oo} = U, \ g_{11} = V, \ g_{22} = ...
0
votes
0
answers
35
views
What is the dark energy & dark matter? [duplicate]
Can anyone explain to me simply what is the dark energy or what is the dark matter. I have been trying to understand it deeply. but I somehow failed.
2
votes
1
answer
302
views
Friedmann equation and model universes
I was studying Barbara Ryden book on modern cosmology, on it's 5th chapter, she introduces the following image:
This image summarises the general behaviour of the Hubble constant. I was wondering, ...
- 97
3
votes
1
answer
527
views
Does $\Lambda$CDM include inflation?
$\Lambda$CDM obviously includes dark energy (the $\Lambda$) as well as cold dark matter (CDM). Does it also include cosmic inflation?
I've not seen a clear answer to this. Wikipedia's article on ...
- 21.4k
2
votes
1
answer
454
views
Why are there a bunch of cosmological coincidences?
There are several cosmological parameters that are more or less of the same order $10^{-60}$ (in Planck unit), namely,
inverse of the age of the universe
$$
\frac{1}{t_0},
$$
Hubble constant
$$
H_0,
$...
- 4,452
3
votes
2
answers
1k
views
Relation between $\Lambda$ and $\Omega_\Lambda$ in $\Lambda\mathrm{CDM}$
In minimal $\Lambda\mathrm{CDM}$, there is a parameter labeled $\Omega_\Lambda$, and current fits place it at around $\left( \Omega_\Lambda \sim 0.73\right)$. Meanwhile, $\Lambda$ enters the Einstein ...
- 399
56
votes
4
answers
4k
views
Are modified theories of gravity credible?
I'm a statistician with a little training in physics and would just like to know the general consensus on a few things.
I'm reading a book by John Moffat which basically tries to state how GR makes ...
- 673