  If inflation can occur only at the energy density V much smaller than the
Planck density, which is the case for many inflationary models based on string
theory, then the probability of quantum creation of a closed or an infinitely
large open inflationary universe is exponentially suppressed for all known
choices of the wave function of the universe. Meanwhile under certain
conditions there is no exponential suppression for creation of topologically
nontrivial compact flat or open inflationary universes. This suggests, contrary
to the standard textbook lore, that compact flat or open universes with
nontrivial topology should be considered a rule rather than an exception.
