Multitracer technique for galaxy bispectrum - An application to
  constraints on non-local primordial non-Gaussianities -
  We explore the use of galaxy bispectra with multitracer technique as a
possible probe of primordial non-Gaussianities. We forecast future constraints
on non-linearity parameters, $f_{\rm NL}^{\rm eq}$ and $f_{\rm NL}^{\rm orth}$,
which respectively characterize the equilateral- and orthogonal-types
primordial bispectra, and show that the multitracer analysis would be effective
with reducing the cosmic-variance noise if the number density of galaxies is
high enough. We find that the measurement of galaxy bispectrum by future galaxy
surveys can reach the constraints on the non-local type primordial
non-Gaussianities to the level severer than current one which has been obtained
by cosmic microwave background observations.
