  In gauge/gravity duality, the bulk double cone geometry has been argued to
account for a key feature of the spectral form factor known as the ramp. This
feature is deeply associated with quantum chaos in the dual field theory. The
connection with the ramp has been demonstrated in detail for two-dimensional
theories of bulk gravity, but it appears natural in higher dimensions as well.
In a general bulk theory the double cone might thus be expected to dominate the
semiclassical bulk path integral for the boundary spectral form factor in the
ramp regime. While other known spacetime wormholes have been shown to be
unstable to brane nucleation when they dominate over known disconnected
(factorizing) solutions, we argue that the double cone is stable to
semiclassical brane nucleation at the probe-brane level in a variety of string-
and M-theory settings. Possible implications for the AdS/CFT factorization
problem are briefly discussed.
