Can we predict the fate of the Universe

Abstract We re-analyze the question of the use of cosmological observations to infer the present state and future evolution of our patch of the universe. In particular, we discuss under which conditions one might be able to infer that our patch will enter an inflationary stage, as a prima facie interpretation of the type Ia supernovae and CMB data would suggest. We then establish a ‘physical’ criterion for the existence of inflation, to be contrasted with the more ‘mathematical’ one recently proposed by Starkman et al., Phys. Rev. Lett. 83 (1999) 1510.