Speaker: Claes Uggla
In this talk I will discuss a minimally coupled scalar field and a perfect fluid in flat FRW cosmology from a dynamical systems perspective. I will illustrate various features, such as mechanisms for attractor solutions, global and local dynamical issues, e.g., connections between slow-roll approximations and center manifolds, and averaging techniques, by addressing a number of examples: A modified Chaplygin gas, monomial potentials, inverse power-law potentials, and I will give conditions on the scalar field potential that give rise to models with an attracting saddle separatrix surface, which describes the evolution of an open set of solutions that continuously deform LambdaCDM cosmology. In the latter case I will also provide cosmographic diagrams that complement the dynamical systems pictures and which facilitate comparisons with LambdaCDM cosmology. Finally, I will situate the present models in a larger perspective, indicating how first principles such as scale-invariance and general covariance give rise to hierarchies of models and symmetries were simpler models act as building blocks for understanding more complicated ones.