CosmoCoffee

David Marsh · Posted: January 19 2012

I have looked at initial conditions in both the CAMB notes, and the referenced paper. There is a correction to

δ γ

in CAMB not present in the paper, which goes as omtau. Is this a higher order correction? If so, why is it necessary, and where is it derived?

I also cannot see the definition of

π r

. I presume it is some multiple of

σ r

(

σ ν

in the reference), but it isn't obvious. The same is true of

G 3

. The definitions also seem absent from arXiv:astro-ph/0203507 on a first glance.

Many thanks in advance to all who can offer help.

Antony Lewis · Posted: January 19 2012

The omtau terms allow for the effect of matter, as opposed assuming pure radiation domination.

You can find maple derivations at

http://camb.info/theory.html

Also somewhat more generally in mathematica at http://camb.info/jrs/

π r

is the (scalar or tensor part of the) neutrino anisotropic stress; scalar definitions should be consistent with the appendix of arXiv:astro-ph/0203507 I think.

David Marsh · Posted: January 20 2012

Thank you so much! I think the mathematica and maple notebooks will be most helpfull.