Assisted coupled quintessence
  We study models of quintessence consisting of a number of scalar fields
coupled to several dark matter components. In the case of exponential
potentials the scaling solutions can be described in terms of a single field.
The corresponding effective logarithmic slope and effective coupling can be
written in a simple form in terms of the individual slopes and couplings of the
original fields. We also investigate solutions where the scalar potential is
negligible, in particular those leading to transient matter dominated
solutions. Finally, we compute the evolution equations for the linear
perturbations which will allow these models to be tested against current and
future observational data.
