Primordial Non-Gaussianity in the Forest: 3D Bispectrum of Ly-alpha Flux
  Spectra Along Multiple Lines of Sight
  We investigate the possibility of constraining primordial non-Gaussianity
using the 3D bispectrum of Ly-alpha forest. The strength of the quadratic
non-Gaussian correction to an otherwise Gaussian primordial gravitational field
is assumed to be dictated by a single parameter fnl. We present the first
prediction for bounds on fnl using Ly-alpha flux spectra along multiple lines
of sight. The 3D Ly-$\alpha$ transmitted flux field is modeled as a biased
tracer of the underlying matter distribution sampled along 1D skewers
corresponding to quasars sight lines. The precision to which fnl can be
constrained depends on the survey volume, pixel noise and aliasing noise
(arising from discrete sampling of the density field). We consider various
combinations of these factors to predict bounds on fnl. We find that in an
idealized situation of full sky survey and negligible Poisson noise one may
constrain fnl ~ 23 in the equilateral limit. Assuming a Ly-alpha survey
covering large parts of the sky (k_{min} = 8 * 10^{-4} Mpc^{-1}) and with a
quasar density of \bar n = 5 * 10^{-3} Mpc^{-2} it is possible to constrain fnl
~ 100 for equilateral configurations. The possibility of measuring fnl at a
precision comparable to LSS studies maybe useful for joint constraining of
inflationary scenarios using different data sets.
