Surviving doomsday and time symmetry
Besides the Big Rip, there is another possible future singularity that would mark the end of a dark energy Universe, that is the so-called Big Freeze singularity. It takes place in certain generalized Chaplygin gas dark energy models and implies freezing of the scale factor of the Universe while the energy density diverges. We argue that quantum effects would smooth out such a singularity and therefore prevent the doomsday that it entails and conjecture that quantum effects would also prevent the emergence of the Big Rip singularity but not the Big Trip phenomenon. The latter future event would be in turn avoided to occur in the observable single Universe described in an infinite time interval but would occur in the Multiverse in such a way that it would make the fundamental particle physics time-symmetric.