The effects of multiple modes and reduced symmetry on the rapidity and robustness of slow contraction

We demonstrate that the rapidity and robustness of slow contraction in homogenizing and flattening the universe found in simulations in which the initial conditions were restricted to non-perturbative variations described by a single Fourier mode along only a single spatial direction are in general enhanced if the initial variations are along two spatial directions, include multiple modes, and thereby have reduced symmetry. Particularly significant are shear effects that only become possible when variations are allowed along two or more spatial dimensions. Based on the numerical results, we conjecture that the counterintuitive enhancement occurs because more degrees of freedom are activated which drive spacetime away from an unstable Kasner fixed point and towards the stable Friedmann-Robertson-Walker fixed point. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

It is demonstrated that the rapidity and robustness of slow contraction in homogenizing and flattening the universe are generally enhanced when initial variations are along two spatial directions, include multiple modes, and have reduced symmetry. Particularly significant are shear effects that only become possible when variations are allowed along two or more spatial dimensions. Based on numerical results, it is conjectured that this counterintuitive enhancement occurs because more degrees of freedom are activated, driving spacetime away from an unstable Kasner fixed point towards the stable Friedmann-Robertson-Walker fixed point.