Einstein's signature in cosmological large-scale structure
  We show how the non-linearity of general relativity generates a
characteristic non-Gaussian signal in cosmological large-scale structure that
we calculate at all perturbative orders in a large scale limit. Newtonian
gravity and general relativity provide complementary theoretical frameworks for
modelling large-scale structure in $\Lambda$CDM cosmology; a relativistic
approach is essential to determine initial conditions which can then be used in
Newtonian simulations studying the non-linear evolution of the matter density.
Most inflationary models in the very early universe predict an almost Gaussian
distribution for the primordial metric perturbation, $\zeta$. However, we argue
that it is the Ricci curvature of comoving-orthogonal spatial hypersurfaces,
$R$, that drives structure formation at large scales. We show how the
non-linear relation between the spatial curvature, $R$, and the metric
perturbation, $\zeta$, translates into a specific non-Gaussian contribution to
the initial comoving matter density that we calculate for the simple case of an
initially Gaussian $\zeta$. Our analysis shows the non-linear signature of
Einstein's gravity in large-scale structure.
