Comment on "Turnaround in Cyclic Cosmology"

Abstract

We comment on a recent paper by L. Baum and P. H. Frampton [Phys. Rev. Lett. 98, 071301 (2007)] where it was argued that the entropy problem can be resolved in a peculiar cyclic universe model through a deflation mechanism (i.e., the universe is fragmented into many disconnected causal patches at the turnaround). We point out that in this cyclic model the Hubble length will become infinity at the turnaround, thus the deflation scenario is not valid.