Cosmology

Question 1

What is the CMB-dipole?

Answer 1

The measured temperature fluctuations forming a dipole on the sky due to the relative motion of the telescope and the CMB rest frame

Question 2

At what wavelength to the CMB radiation peak?

Answer 2

2 mm

Question 3

Decoupling of photons from matter occurs when the mean free time of the photons is larger than
the characteristic time-scale of expansion. At what redshift did this occur?

Answer 3

z=1100

Question 4

Hubble scale

Answer 4

a cosmological distance unit equal to the reciprocal of the Hubble constant times the speed of light; see derivation below

H_0^(-1)=t_H*c=4.3 Gpc

Question 5

For what redshifts did reionization occur?

Answer 5

Between 7 and 20

Question 6

What is the Sach-Wolfe effect?

Answer 6

Photons starting from overdense regions are redshifted. The integrated SW-effect (10 deg scale) is about gravity wells changing dept during the time of visit for a photon.

Question 7

What is the Rees-Sciama effect?

Answer 7

Photon traversing varying non-linear gravitational. It can be caused by collapsing clusters and is 5-10 arcmin large

Question 8

How strong is the polarized part of the CMB?

Answer 8

About 10% of the anistropies, i.e. 10^-6 of T_CMB

Question 9

Alan Guth introduced inflation theory in 1981. What problems does that solve

Answer 9

1. Flatness problem. F.E. curvature*a^2=const. If a started very small and quickly increased to unit scale the curvature need not have been fine tuned.
2. Horizon problem. Quick expansion made anistropies smaller, in proportion to their previous size.
3. Monopoles. Knots in magnetic field are just very uncommon.