Hi again, Bartek, everyone,
On Tue, 7 Jan 2003, Bartosz Lew wrote:
what is the true meaning of P(k) ???
It only has a true meaning if:
(1) the curvature of comoving space is zero (it is perfectly flat)
(2) the topology of comoving space is an equal-sided, right-angled, hypertorus
If either (1) or (2) is false, then P(k) is only an *approximation*, and if you forget this you may make errors. (If everyone makes the same error, it is still an error. It's OK politically, but not OK scientifically.)
I did a quick search using
"power spectrum density perturbations"
and found a fairly standard definition by Pedro Viana:
http://nedwww.ipac.caltech.edu/level5/Viana/Viana2_1.html
What seems to be missing is the definition of delta_[k (scalar)] in terms of delta_[k (vector)].
My guess is that
|delta_[k (scalar)]|^2 in the definition of P(k)
should be replaced by
< | delta_[k (vector)] | ^2 >
where the average is taken over all [k (vector)] pointing in different directions, for the same fixed magnitude of k > 0 .
But you should check, where you take an averages or absolute value can make a difference...
boud