Causality and entropic arguments pointing to a null Big Bang hypersurface

Ettore Minguzzi

I propose a causality argument in order to solve the homogeneity problem of cosmology. The solution is based on the replacement of the spacelike Big Bang boundary with a null boundary behind which stays a chronology violating region.
This solution requires a suitable tilting of the light cones near the null boundary and thus is based more on the behavior of the light cones and hence on causality than on the scale factor (expansion). It is then shown that this solution may allow to solve the entropy problem of cosmology. The philosophical connection of this picture with Augustine of Hyppo famous discussion of time and creation is also commented.