  We investigate the cosmological signatures of instantons mediating tunneling
between de Sitter minima. For generic potentials the Coleman-de Luccia
instanton does not necessarily exist; when it does not, the instanton which
contributes to the decay rate is the trivial constant solution, known as the
Hawking-Moss instanton. With the aid of a toy model we interpret this solution
and describe the resulting cosmology. In neither the Coleman-de Luccia nor
Hawking-Moss case can the resulting cosmology be closed. An observation of
significant positive curvature would therefore rule out the possibility that
our universe arose from any transition from a neighboring minimum in the
string-theory landscape.
