We first revisit Hartle and Hawking’s path integral derivation of
Hawking radiation. In the first point of view, we interpret that a
particle-antiparticle pair is created and the negative energy
antiparticle falls into the black hole. On the other point of view, a
particle inside the horizon, or beyond the Einstein-Rosen bridge,
tunnels to outside the horizon, where this computation requires the
analytic continuation of the time. These two faces of the Hawking
radiation process can be extended to not only particles but also fields.
As a concrete example, we study the thin-shell tunneling process; by
introducing the antishell as a negative tension shell, we can give the
consistent interpretation for two pictures, where one is a tunneling
from inside to outside the horizon using instantons, while the other is
a shell-antishell pair-creation. This shows that the Euclidean path
integral indeed carries vast physical implications not only for
perturbative, but also for non-perturbative processes.