Dynamics of multi-scalar-field cosmological models and assisted inflation - art. no. 023517

We investigate the dynamical properties of a class of spatially homogeneous and isotropic cosmological models containing a barotropic perfect fluid an d multiple scalar fields with independent exponential potentials. We show t hat the assisted inflationary scaling solution is the global late-time attr actor for the parameter values for which the model is inflationary, even wh en curvature and barotropic matter are included. For all other parameter va lues the multi-held curvature scaling solution is the global late-time attr actor(in these asymptotically stable solutions the curvature is not dynamic ally negligible). Consequently, we find that in general all of the scalar f ields in multi-held models with exponential potentials are non-negligible i n late-time behavior, contrary to what is commonly believed. The early-time and intermediate behavior of the models is also studied. In particular, n- scalar field models are investigated and the structure of the saddle equili brium points corresponding to inflationary m-field scaling solutions and no n-inflationary In-field matter scaling solutions are also studied (where m< n), leading to interesting transient dynamical behavior perhaps associated with new physical scenarios of potential importance.