The Limited Accuracy of Linearized Gravity
  Standard cosmological models rely on an approximate treatment of gravity,
utilizing solutions of the linearized Einstein equations as well as physical
approximations. In an era of precision cosmology, we should ask: are these
approximate predictions sufficiently accurate for comparison to observations,
and can we draw meaningful conclusions about properties of our Universe from
them? In this work we examine the accuracy of linearized gravity in the
presence of collisionless matter and a cosmological constant utilizing fully
general relativistic simulations. We observe the gauge-dependence of
corrections to linear theory, and note the amplitude of these corrections. For
perturbations whose amplitudes are in line with expectations from the standard
$\Lambda$CDM model, we find that the full, general relativistic metric is
well-described by linear theory in Newtonian and harmonic gauges, while the
metric in comoving-synchronous gauge is not. For the largest observed
structures in our Universe, our results suggest that corrections to linear
gravitational theory can reach or surpass the percent-level.
