  We employ double holography to examine a system of two entangled gravitating
universes that live on two codimension-one branes in an asymptotically AdS$_3$
spacetime with two disjoint conformal boundaries. There are distinct brane
configurations depending on the temperature of the thermofield double (TFD)
state between the left and right systems. The topology transition between two
branes is naturally identified with the emergence of an Einstein-Rosen bridge
connecting the two entangled universes. This doubly holographic construction
offers a holographic perspective on gravitational collapse and black hole
formation in brane universes. Through this holographic framework, we analyze
the quantum information structure of the two gravitating universes.
Specifically, we calculate the mutual information between defects present in
the boundary theories on the left and right sides. Furthermore, we investigate
the decoupling process in the Hayden-Preskill protocol applied to the two
copies of the defect field theory and discuss the interpretation of the
Yoshida-Kitaev decoding protocol.
