Q: "on problem 4, part b, which universe should we assume this is, k=0,-1,+1? i'd want to use that information to find q0 (deceleration parameter) from omega0, since that is a needed quantity in eq (27.101)."
A: Are you certain you need a particular value? If you can not proceed in any other way, why not assume a flat universe with zero cosmological constant, for concreteness.
Q: "I don't understand the Greek letters in problem 1. Does X = d/R? Is it the co-moving coordinate? I don't know if you can help or if this is just part of solving the problem."
A: I think the way to think about problem 1 is that I am asking you to find a change of coordinates such that, in this new coordinate system, the FRW metric takes the form in equations 1 and 2. X is somehow related to x and/or t ; you need to figure out what the mapping is that transforms the metric to the forms listed.
and
, what is the proper distance to this
cluster from Earth [in Mpc]? Consider the cases of
,
corresponding to
, respectively."
Q: "for Problem 4, in the relation derived in part a there exists an extinction term, but in part b we assume just that extintion has been corrected for, when finding the value of H can we assume that there is no extinction or should we estimate it...?"
A: That is correct: in part b you can assume the extinction has been corrected. If you like, you can assume "a=0" for part b.
