Non-relativistic spacetimes with cosmological constant

Recent data on supernovae favour high values of the cosmological constant. Spacetimes with a cosmological constant have non-relativistic kinematics qu ite different from Galilean kinematics. de Sitter spacetimes, vacuum soluti ons of Einstein's equations with a cosmological constant, reduce in the non -relativistic limit to Newton-Hooke spacetimes, which are non-metric homoge neous spacetimes with non-vanishing curvature. The whole non-relativistic k inematics would then be modified, with possible consequences to cosmology, and in particular to the missing-mass problem.