Cosmology with anisotropic galaxy clustering from the combination of
  power spectrum and bispectrum
  The apparent anisotropies of the galaxy clustering in observable redshift
space provide a unique opportunity to simultaneously probe cosmic expansion and
gravity on cosmological scales via the Alcock--Paczynski effect and
redshift-space distortions. While the improved theoretical models have been
proposed and developed to describe the apparent anisotropic clustering at
weakly non-linear scales, the applicability of these models is still limited in
the presence of the non--perturbative smearing effect caused by the randomness
of the relative velocities. Although the cosmological constraint from the
anisotropic clustering will be certainly improved with a more elaborate
theoretical model, we here consider an alternative way by using the statistical
power of both the power spectrum and bispectrum at large scales. Based on the
Fisher matrix analysis, we estimate the benefit of combining the power spectra
and bispectra, finding that the constraints on the cosmic expansion and growth
of structure will be improved by a factor of two. This compensates for the loss
of constraining power using the power spectrum alone due to the randomness of
the relative velocities.
