Robustness of the quintessence scenario in particle cosmologies

We study the robustness of the quintessence tracking scenario in the context of more general cosmological models that derive from high-energy physics. We consider the effects of the inclusion of multiple scalar fields, corrections to the Hubble expansion law (such as those that arise in brane cosmological models), and potentials that decay with expansion of the universe. We find that in a successful tracking quintessence model die average equation of state must remain nearly constant. Overall, the conditions for successful tracking become more complex in these more general settings. Tracking can become more fragile in the presence of multiple scalar fields, and more stable when temperature-dependent potentials are present. Interestingly, though, most of the cases where tracking is disrupted are those in which the cosmological model is itself nonviable due to other constraints. In this sense tracking remains robust in models that are cosmologically viable.