  The measurement of cosmological parameters is investigated in a
representation of the least-action method that uses a redshift-space dataset to
simultaneously constrain the real-space fields $\delta$,$\b v$. This method is
robust in recovering the entire evolution of the matter density contrast and
peculiar velocities of galaxies in real space from current galaxy redshift
surveys. The main strength of the method is that it permits us to break the
degeneracy of the parameters $b$ and $\Omegam$ (customarily measured in the
ratio $\beta\equiv \Omegam^{0.6}/b$ from redshift-space distortions), and these
are evaluated in the current context separately. The procedure provides a
simple numerical means to extract as much information as possible from a given
sample, in the simplest linear bias model, before resorting to cosmic
complementarity to resolve the degeneracy in the measurement of $\Omegam$. The
same premise applies to more sophisticated choices of bias models. We construct
a likelihood parameter $\lambda(b,\Omegam)$ to evaluate the relative likelihood
of different values of $b$ and $\Omegam$. The method is applied to the \iras
redshift survey with a low-resolution Gaussian smoothing length of 1200 \km
within a spherical region $x_{\rm max} \sim 15,000$ \km and the reconstructed
velocity field is then compared with POTENT-reconstructed velocities from the
Mark III radial-velocity dataset within a radius $\sim 5000$ \km, which have
been suitably prepared to account for Malmquist bias and other systematic
errors. The analysis yields a likelihood for the parameters that is overall
consistent with $\Omegam\approx 0.3$ and $b\approx 1.1$, thus lending support
to a non-vanishing cosmological constant $\Omega_{\Lambda}\approx 0.7$ in a
flat universe.
