These methods use the mean motions induced by the large-scale
mass distributions on scales of several megaparsecs and above.
They are based on GI in the linear regime
and approximate extensions into the mildly-nonlinear regime.
The different matter contributions to
m are relevant,
such as ``cold'' and ``hot'' dark matter (see
[33] for a review),
but the cosmological constant is not involved.
The statistical nature of the initial fluctuations has to be specified in
some cases; it is commonly assumed to be a Gaussian random field.
The initial fluctuation power spectrum is characterized by the power
index n
on large scales, by a specific shape (e.g., as predicted by
CDM theory), and by its amplitude, e.g., via
8,
the rms fluctuation in top-hat spheres of radius
8 h-1Mpc.
Galaxy biasing is expected to enter in a simpler manner on these larger
scales, but is still an important unknown. In the common simplified
treatments it is modeled as a linear biasing relation between the density
fluctuations of galaxies and mass,
g = b
, with different
biasing parameters for different galaxy types: biras,
bopt, etc.
However, non-trivial properties of the biasing scheme may be important.