Direct Determination of Expansion History Using Redshift Distortions
  We investigate the direct determination of expansion history using redshift
distortions without plugging into detailed cosmological parameters. The
observed spectra in redshift space include a mixture of information:
fluctuations of density-density and velocity-velocity spectra, and distance
measures of perpendicular and parallel components to the line of sight.
Unfortunately it is hard to measure all the components simultaneously without
any specific prior assumption. Common prior assumptions include a
linear/quasi-linear model of redshift distortions or a model for the shape of
the power spectra, which eventually breaks down on small scales at later epochs
where nonlinear structure formation disturbs coherent growth. The degeneracy
breaking, between the effect of cosmic distances and redshift distortions for
example, depends on the prior we assume. An alternative approach is to utilize
the cosmological principle inscribed in the heart of the
Friedmann-Lematre-Robertson-Walker (hereafter FLRW) universe, that is, the
specific relation between the angular diameter distance and the Hubble
parameter, in this degeneracy breaking. We show that utilizing this FLRW prior
early in the step of distinguishing the distance effect from redshift
distortions helps us improve the detectability of power spectra and distance
measures with no leaning on a combination of other experiments.
