I am concerned about equations 2, 5 and 6 on page 2 of arXiv:astro-ph/0606028.
The paper refers them to the book by Peebles which I don't have access to at this point.
I believe that these equations are standard enough to have been derived in other standard cosmology books as well like Dodelson's or Liddle and Lyth (which I have access to).
But on searching in the above two books I don't see these there. I wonder if they are garbed in a different notation/terminology which is making it hard to detect. I would be glad if someone can point to the exact reference.
So are these 3 equations fully General Relativistic equations but valid in only flat FRW metric?