Nature 302, 505 - 506 (07 April 1983); doi:10.1038/302505a0

The impossibility of a bouncing universe

Alan H. Guth^* & Marc Sher^†

^*Center for Theoretical Physics, Laboratory for Nuclear Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
^†Department of Physics, University of California, Irvine, California 92717, USA

Petrosian¹ has recently discussed the possibility that the restoration of symmetry at grand unification in a closed contracting Robertson−Walker universe could slow down and halt the contraction, causing the universe to bounce. He then went on to discuss the possibility that our universe has undergone a series of such bounces. We disagree with this analysis. One of us (M.S.) has already shown² that if a contracting universe is dominated by radiation, then a bounce is impossible. We will show here two further results: (1) entropy considerations imply that the quantity S (defined in ref. 1 and below), which must decrease by 10⁷⁵ to allow the present Universe to bounce, can in fact decrease by no more than a factor of 2; (2) if the true vacuum state has zero energy density, then a universe which is contracting in its low temperature phase can never complete a phase transition soon enough to cause a bounce.

References

1.	Petrosian, V. Nature 298, 805 (1982). | ISI |
2.	Sher, M. Phys. Rev. D22, 2989 (1980). | Article | ISI | ChemPort |
3.	Weinberg, S. Gravitation and Cosmology (Wiley, New York, 1972).
4.	Huang, K. Statistical Mechanics Chs 8, 9 (Wiley, New York, 1963).