Measuring BAO and non-Gaussianity via QSO clustering
  Our goals are (i) to search for BAO and large-scale structure in current QSO
survey data and (ii) to use these and simulation/forecast results to assess the
science case for a new, >10x larger, QSO survey. We first combine the SDSS, 2QZ
and 2SLAQ surveys to form a survey of ~60000 QSOs. We find a hint of a peak in
the QSO 2-point correlation function, xi(s), at the same scale (~105h^-1 Mpc)
as detected by Eisenstein et al (2005) in their sample of DR5 LRGs but only at
low statistical significance. We then compare these data with QSO mock
catalogues from the Hubble Volume simulation used by Hoyle et al (2002) and
find that both routes give statistical error estimates that are consistent at
~100h^-1 Mpc scales. Mock catalogues are then used to estimate the nominal
survey size needed for a 3-4 sigma detection of the BAO peak. We find that a
redshift survey of ~250000 z<2.2 QSOs is required over ~3000 deg^2. This is
further confirmed by static log-normal simulations where the BAO are clearly
detectable in the QSO power spectrum and correlation function. The nominal
survey would on its own produce the first detection of, for example,
discontinuous dark energy evolution in the so far uncharted 1<z<2.2 redshift
range. A survey with ~50% higher QSO sky densities and 50% bigger area will
give an ~6sigma BAO detection, leading to an error ~60% of the size of the BOSS
error on the dark energy evolution parameter, w_a.
  Another important aim for a QSO survey is to place new limits on primordial
non-Gaussianity at large scales, testing tentative evidence we have found for
the evolution of the linear form of the combined QSO xi(s) at z~1.6. Such a QSO
survey will also determine the gravitational growth rate at z~1.6 via z-space
distortions, allow lensing tomography via QSO magnification bias while also
measuring the exact luminosity dependence of small-scale QSO clustering.
