  A scale invariant, Weyl geometric, Lagrangian approach to cosmology is
explored, with a a scalar field phi of (scale) weight -1 as a crucial
ingredient besides classical matter \cite{Tann:Diss,Drechsler:Higgs}. For a
particularly simple class of Weyl geometric models (called {\em Einstein-Weyl
universes}) the Klein-Gordon equation for phi is explicitly solvable. In this
case the energy-stress tensor of the scalar field consists of a vacuum-like
term Lambda g_{mu nu} with variable coefficient Lambda, depending on matter
density and spacetime geometry, and of a dark matter like term. Under certain
assumptions on parameter constellations, the energy-stress tensor of the
phi-field keeps Einstein-Weyl universes in locally stable equilibrium. A short
glance at observational data, in particular supernovae Ia (Riess ea 2007),
shows interesting empirical properties of these models.
