  Large surveys for Lyman-alpha emitting (LAE) galaxies have been proposed as a
new method for measuring clustering of the galaxy population at high redshift
with the goal of determining cosmological parameters. However, Lyman-alpha
radiative transfer effects may modify the observed clustering of LAE galaxies
in a way that mimics gravitational effects, potentially reducing the precision
of cosmological constraints. For example, the effect of the linear
redshift-space distortion on the power spectrum of LAE galaxies is potentially
degenerate with Lyman-alpha radiative transfer effects owing to the dependence
of observed flux on intergalactic medium velocity gradients. In this paper, we
show that the three-point function (bispectrum) can distinguish between
gravitational and non-gravitational effects, and thus breaks these
degeneracies, making it possible to recover cosmological parameters from LAE
galaxy surveys. Constraints on the angular diameter distance and the Hubble
expansion rate can also be improved by combining power spectrum and bispectrum
measurements.
