Non–Relativistic Spacetimes with Cosmological Constant

Recent data on supernovae favor high values of the cosmological constant. Spacetimes with a cosmological constant have non–relativistic kinematics quite different from Galilean kinematics. De Sitter spacetimes, vacuum solutions of Einstein’s equations with a cosmological constant, reduce in the non–relativistic limit to Newton–Hooke spacetimes, which are non–metric homogeneous spacetimes with non–vanishing curvature. The whole non– relativistic kinematics would then be modified, with possible consequences to cosmology, and in particular to the missing–mass problem.