Generalized dark energy interactions with multiple fluids
  In the search for an explanation for the current acceleration of the
Universe, scalar fields are the most simple and useful tools to build models of
dark energy. This field, however, must in principle couple with the rest of the
world and not necessarily in the same way to different particles or fluids. We
provide the most complete dynamical system analysis to date, consisting of a
canonical scalar field conformally and disformally coupled to both dust and
radiation. We perform a detailed study of the existence and stability
conditions of the systems and comment on constraints imposed on the disformal
coupling from Big-Bang Nucleosynthesis and given current limits on the
variation of the fine-structure constant.
