Cosmic alignment of the aether
  In Einstein-aether theory and Horava gravity, a timelike unit vector is
coupled to the spacetime metric. It has previously been shown that in an
exponentially expanding homogeneous, isotropic background, small perturbations
of the vector relax back to the isotropic frame. Here we investigate large
deviations from isotropy, maintaining homogeneity. We find that, for generic
values of the coupling constants, the aether and metric relax to the isotropic
configuration if the initial aether hyperbolic boost angle and its time
derivative in units of the cosmological constant are less than something of
order unity. For larger angles or angle derivatives, the behavior is strongly
dependent on the values of the coupling constants. Generally there is runaway
behavior, in which the anisotropy increases with time, and/or singularities
occur.
