Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Islands and mixed states in closed universes   We investigate the appearance of islands when a closed universe with gravity
is entangled with a non-gravitating quantum system. We use braneworlds in
three-dimensional multiboundary wormhole geometries as a model to explore what
happens when the non-gravitating system has several components. The braneworld
can be either completely contained in the entanglement wedge of one of the
non-gravitating systems or split between them. In the former case, entanglement
with the other system leads to a mixed state in the closed universe, unlike in
simpler setups with a single quantum system, where the closed universe was
necessarily in a pure state. We show that the entropy of this mixed state is
bounded by half of the coarse-grained entropy of the effective theory on the
braneworld.

1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex