A generic prediction of inflation is that the thermalized region we inhabit is spatially infinite. Thus, it contains an infinite number of regions of the same size as our observable universe, which we shall denote as regions. We argue that the number of possible histories which may take place inside of an region, from the time of recombination up to the present time, is finite. Hence, there are an infinite number of regions with identical histories up to the present, but which need not be identical in the future. Moreover, all histories which are not forbidden by conservation laws will occur in a finite fraction of all regions. The ensemble of regions is reminiscent of the ensemble of universes in the many-world picture of quantum mechanics. An important difference, however, is that other regions are unquestionably real.
- Received 16 February 2001
- Published 26 July 2001
© 2001 The American Physical Society