Cosmic Background Radiation and DM

[geordief]

Is there any connection between the Cosmic Background Radiation and Dark Matter.

Dark Matter apparently accounts for a lot of the overall matter in the Universe..

Should its presence be evident in the analysis of the CBR ?

 

Or would its  temperature profile around the time of the BB  be indistinguishable  from that of ordinary matter?

 

Are there any other ways  analyses of the CBR  could shed light on the DM mystery?

[swansont]

Any “background” DM would likely not have the same temp as the microwaves, just as background neutrinos have a different temperature. I suspect that DM never decoupled, or did so a tiny fraction of a second after the BB. Unlike photons and neutrinos.

https://en.wikipedia.org/wiki/Cosmic_neutrino_background

[MigL]

The CMB is an Electromagnetic phenomenon.
We don't expect Dark Matter to have any EM effects that can be detected.

[J.C.MacSwell]

38 minutes ago, MigL said:

The CMB is an Electromagnetic phenomenon.
We don't expect Dark Matter to have any EM effects that can be detected.

Gravitationally? DM should effect lensing of EM radiation should it not?

I'm trying to think of an observable effect if any when the CMBR is anisotropic wrt the frame of the DM vs when it is not.

Edited December 24, 2020 by J.C.MacSwell

[swansont]

I’m not sure lensing would be detected. The radiation is isotropic, and it’s not obvious to me there would be any wavelength changes.

 

[J.C.MacSwell]

10 hours ago, swansont said:

I’m not sure lensing would be detected. The radiation is isotropic, and it’s not obvious to me there would be any wavelength changes.

 

All DM is in a frame in which the CMBR is isotropic? That would pretty much require most Galaxies to be.

[MigL]

Don't let the artificially colored pictures fool you.
The CMB is isotropic ( same in all directions ) to 2 parts in 10 000.

You would start seeing deviations from 2.7⁰ K after the 4th decimal place.

[swansont]

6 hours ago, J.C.MacSwell said:

All DM is in a frame in which the CMBR is isotropic? That would pretty much require most Galaxies to be.

How is that connected to lensing?

Lensing requires a source in a particular direction. The isotropy means that there is radiation from all directions. The signal to noise would be tiny.

 

[J.C.MacSwell]

7 hours ago, swansont said:

How is that connected to lensing?

Lensing requires a source in a particular direction. The isotropy means that there is radiation from all directions. The signal to noise would be tiny.

 

Isotropy means it's evenly from all directions. 

 

13 hours ago, MigL said:

Don't let the artificially colored pictures fool you.
The CMB is isotropic ( same in all directions ) to 2 parts in 10 000.

You would start seeing deviations from 2.7⁰ K after the 4th decimal place.

Only from a frame where the frame is at rest wrt the CMBR, 

Any Galaxy moving wrt that will measure it as anisotropic.

[swansont]

40 minutes ago, J.C.MacSwell said:

Isotropy means it's evenly from all directions. 

Yes, and how does this have an effect on lensing?

40 minutes ago, J.C.MacSwell said:

Only from a frame where the frame is at rest wrt the CMBR, 

Any Galaxy moving wrt that will measure it as anisotropic.

You can remove that bias. Anisotropy would remain after the correction 

[J.C.MacSwell]

11 minutes ago, swansont said:

Yes, and how does this have an effect on lensing?

 

I don't know.

On 12/24/2020 at 1:30 PM, J.C.MacSwell said:

Gravitationally? DM should effect lensing of EM radiation should it not?

I'm trying to think of an observable effect if any when the CMBR is anisotropic wrt the frame of the DM vs when it is not.

 

15 minutes ago, swansont said:

 

You can remove that bias. Anisotropy would remain after the correction 

You can calculate it out. That doesn't physically remove it. Normal matter would experience a drag effect when moving wrt the CMBR.

The measurable anisotropy of the CMBR is frame dependant.

I know the minimum anisotropy is commonly referred to as the CMBR anisotropy. This is not what I'm referring to.  I'm referring to the fact that Galaxies typically are at some velocity wrt the CMBR, and therefore their constituent DM must be as well. There may be no measurable effect, but like the drag for normal matter mentioned above, there could be. I'm not sure exactly what it would be if it could be measured, but we do know EMR is affected by gravity.