  For O(4)-symmetric instantons, there are two complementary interpretations
for their analytic continuations. One is the nothing-to-something
interpretation, where the initial and final hypersurfaces are disconnected by
Euclidean manifolds. The other is the something-to-something interpretation,
introduced by Brown and Weinberg, where the initial and final hypersurfaces are
connected by the Euclidean manifold. These interpretations have their own pros
and cons and hence they are complementary. In this paper, we consider analytic
continuations of thin-shell instantons that have less symmetry, i.e., the
spherical symmetry. When we consider the
Farhi-Guth-Guven/Fischler-Morgan-Polchinski tunneling, the
something-to-something interpretation has been used in the usual literature. On
the other hand, we can apply the nothing-to-something interpretation with some
limited conditions. We argue that for both interpretations, we can give the
consistent decay rate. As we apply and interpret what follows the
nothing-to-something interpretation, a stationary black hole can emit an
expanding shell that results in a spacetime without a singularity or event
horizon.
