Tagged Questions
4
votes
2answers
68 views
Cosmological triangle with PLANCK results
Is there an updated version of the cosmological triangle with recent PLANCK results included?
1
vote
0answers
15 views
CMB anisotropies and tightly coupled limit
Sorry if this is a technical question. I am studying the origin of CMB anisotropies and the tightly coupled limit of the Boltzmann equations. We have a fluid composed of ionized electrons and photons.
...
4
votes
1answer
71 views
How the CMB anisotropy is linked to the existence of cold dark matter and dark energy?
After the data from the cosmic microwave background has been collected by WMAP or Planck, what types of analysis is needed to conduct in order to deduce the cold dark matter density and the ...
4
votes
2answers
295 views
Why cosmic background radiation is not ether?
why cosmic background radiation is not ether? I mean it's everywhere and it' a radiation then we can measure Doppler effect by moving with a velocity.
1
vote
1answer
60 views
What does Planck/WMAP/COBE actually measure when studying the CMB?
I have been reading a lot about Cosmological experiments such as Planck or WMAP that aim to investigate the CMB's power spectrum. I am unclear though as to what theses sky surveys actually measure, is ...
5
votes
2answers
147 views
What's the significance of large-scale anomalies in CMB
What's the significance of large-scale anomalies in CMB that are confirmed by Planck? I've read somewhere that the cold spots can provide support for string theory or it may be due to a parallel ...
3
votes
1answer
97 views
Inflation and scalar spectral index
I've been reading that the results from the Planck satellite constrain a number called the "scalar spectral index" to be 0.96 rather than 1 at the 5-sigma level.
This is supposed to be big news, but ...
1
vote
2answers
135 views
Is cosmic background radiation dark-matter and/or dark-energy?
Dumb question alert: Is it possible that the cosmic background radiation might be the source of dark-matter and/or dark-energy? What is the mass of the background radiation in the known universe?
1
vote
1answer
182 views
Relation between multipole moment and angular scale of CMB
What is the relation between multipole moment $l$ and angular scale $\theta$ of the Cosmic Microwave Background? Somewhere on the web I found that $\theta\propto\frac{180^{\circ}}{l}$ but I need exact ...
1
vote
1answer
82 views
How precisely can we date the recombination?
The early universe was hot and opaque. Once it cooled enough, protons and electrons were able to form hydrogen atoms. This made the universe transparent, and was known as recombination. We can see the ...
3
votes
1answer
129 views
How could we experience multiverse through cosmic background radiation?
I'm reading a book about string theory, and it tells me in the future it could be possible to detect existence of other bubble universes through cosmic background radiation. Is this true? What could ...
1
vote
2answers
72 views
$\Omega_{r}$ from WMAP results?
To do some Friedmann-Lemaître cosmology calculations, I would like to know an estimation of $\Omega_{r_0}$ ($\Omega$ radiation today). WMAP 7 give estimation of $\Omega_{b}$, $\Omega_{c}$ and ...
7
votes
1answer
261 views
Plotting the CMB power spectrum - Why $C_\ell \ell (\ell+1)$ rather than only $C_\ell$?
I can't find any convincing answer for the following question :
Why do we always (or often) plot the CMB power spectrum in this way?
I mean the y axis is $C_\ell \ell (\ell+1)$ and not only ...
0
votes
1answer
126 views
Proportion of energy compared to mass in universe
In Wikipedia (http://en.wikipedia.org/wiki/Dark_matter), there is a picture that shows us the proportion of matter and energy in the current universe - CMB.
It seems to suggest there is nothing that ...
6
votes
3answers
157 views
Where does the light of the Big Bang come from?
I'm wondering whether the residual light of the Big Bang comes from one particular direction and what possibilities do we have to detect its position?
2
votes
2answers
158 views
What are the limitations of the FLRW metric?
I was wondering, given how in any other area of life making an explosion spherically symmetric is more or less impossible is there any reason to expect that the universe is? I appreciate that the FLRW ...
3
votes
2answers
204 views
Big Bang and Cosmic microwave background radiation?
One of the experimental evidence that supports the theory of big bang is cosmic microwave background radiation (CMBR). From what I've read is that CMBR is the left over radiation from an early stage ...
5
votes
2answers
561 views
What is the cosmic “Axis of Evil” problem?
What is the cosmic "axis of evil" problem?
Apparently it is a more modern version of the old cluster mass discrepancy problem, where masses determined by gravitational lensing are always higher than ...
9
votes
2answers
471 views
Why can we see the cosmic microwave background (CMB)?
I understand that we can never see much farther than the farthest galaxies we have observed. This is because, before the first galaxies formed, the universe was opaque--it was a soup of subatomic ...
12
votes
2answers
531 views
What exactly is meant by the “Gaussianity” of CMBR?
What does it mean when we say that the CMBR is mostly gaussian? What are non-gaussianities in CMBR? How does evaluation of 3-point correlation functions of the inflaton field tells us that there is ...
4
votes
1answer
731 views
Where does CMB come/emit from?
Where exactly does CMB come from. I've seen it in documentaries as a huge sphere with Earth in the middle. But if all this radiation was ejected from the start of the universe some time after the big ...
