Qualitative study of perfect-fluid   Friedmann-Lema\^{\i}tre-Robertson-Walker models with a cosmological constant
  The evolution of spatially homogeneous and isotropic cosmological models containing a perfect fluid with equation of state p=w\rho\ and a cosmological constant \Lambda\ is investigated for arbitrary combinations of w and \Lambda, using standard qualitative analysis borrowed from classical mechanics. This approach allows one to consider a large variety of situations, appreciating similarities and differences between models, without solving the Friedmann equation, and is suitable for an elementary course in cosmology. 
Sebastiano Sonego and Vittorino Talamini
physics.ed-ph gr-qc