Relativistic cosmological large scale structures at one-loop
  The large scale structure bispectrum in the squeezed limit couples large with
small scales. Since relativity is important at large scales and non-linear loop
corrections are important at small scales, the proper calculation of the
observed bispectrum in this limit requires a non-linear relativistic
calculation. We compute the matter bispectrum in general relativity in the weak
field approximation. The calculation is as involved as existing second-order
results. We find several differences with the Newtonian calculation such as the
non-cancellation of IR divergences, the need to renormalize the background, and
the fact that initial conditions must be set at second order in perturbation
theory. For the bispectrum, we find relativistic corrections to be as large as
the newtonian result in the squeezed limit. In that limit relativistic one-loop
contributions, which we compute for the first time, can be as large as tree
level results and have the same $1/k^2$ dependence as a primordial local
non-Gaussianity signal where $k$ is the momentum approaching zero. Moreover, we
find the time dependence of the relavistic corrections to the bispectrum to be
the same as that of a primordial non-Gaussianity signal.
