  We argue a scenario motivated by the context of string landscape, where our
universe is produced by a new vacuum bubble embedded in an old bubble and these
bubble universes have not only different cosmological constants, but also their
own different gravitational constants. We study these effects on the primordial
curvature perturbations. In order to construct a model of varying gravitational
constants, we use the Jordan-Brans-Dicke (JBD) theory where different
expectation values of scalar fields produce difference of constants. In this
system, we investigate the nucleation of bubble universe and dynamics of the
wall separating two spacetimes. In particular, the primordial curvature
perturbation on superhorizon scales can be affected by the wall trajectory as
the boundary effect. We show the effect of gravitational constant in the
exterior bubble universe can provide a peak like a bump feature at a large
scale in a modulation of power spectrum.
