Disformal vectors and anisotropies on a warped brane
  The Maxwell action is conformally invariant and classically ignorant of
conformally flat metrics. However, if the vector lives in a disformal metric---
as it does if residing upon a moving brane---this is no longer true. The
disformal coupling is then mediated by a Dirac-Born-Infeld scalar field. Here a
systematic dynamical system analysis is developed for anisotropic Bianchi I
cosmology with a massive disformally coupled vector field. Several new fixed
points are found, including anisotropic scaling solutions. The presented
formalism here presented can be conveniently applied to general scenarios with
or without extra dimensional motivations. This is illustrated here by
performing a complete analysis with simple assumption that both the potentials
and the warp factor for the brane are (nearly) exponential. In that case, the
anisotropic fixed points are either not attractors, do not describe
accelerating expansion or else they feature too large anisotropies to be
compatible with observations. Nonetheless, viable classes of models exist where
isotropy is retained due to rapid oscillations of the vector field, thus
providing a possible realisation of disformally interacting massive dark
matter.
