I Cosmological perturbations and CMBR anisotropies

[Ranku]

CMBR anisotropies are imprinted by cosmological perturbations. What contributed to these original perturbations - is it inflation alone, or does it include baryons, dark matter, neutrinos and dark energy?

 

[Ibix]

It isn't inflation per se. Its source is quantum randomness when the universe was very compact, meaning that the initial density was slightly non-uniform on very small scales. This was rapidly scaled up by inflation and later more slowly by expansion to give the medium scale anisotropy we see today.

Remember that this is all very theoretical.

 

[Ranku]

Its source is quantum randomness when the universe was very compact, meaning that the initial density was slightly non-uniform on very small scales.

So, what are the 'constituents' of initial density upon which quantum randomness operates?

This was rapidly scaled up by inflation and later more slowly by expansion to give the medium scale anisotropy we see today

In the post-inflation universe, do the other constituents of the universe, such as baryons, dark matter, etc., contribute to the anisotropy?

 

[Ibix]

So, what are the 'constituents' of initial density upon which quantum randomness operates?

The inflaton field. When the energy density drops low enough this condenses into normal matter and radiation.

In the post-inflation universe, do the other constituents of the universe, such as baryons, dark matter, etc., contribute to the anisotropy?

Yes - ultimately causing some overdense regions to collapse into stars and planets. And it's its stress-energy in the universe that makes it an expanding universe in the first place.