  We construct new Euclidean wormhole solutions in AdS(d+1) and discuss their
role in UV-complete theories, without ensemble averaging. The geometries are
interpreted as overlaps of GHZ-like entangled states, which arise naturally
from coarse graining the density matrix of a pure state in the dual CFT. In
several examples, including thin-shell collapsing black holes and pure black
holes with an end-of-the-world brane behind the horizon, the coarse-graining
map is found explicitly in CFT terms, and used to define a coarse-grained
entropy that is equal to one quarter the area of a time-symmetric apparent
horizon. Wormholes are used to derive the coarse-graining map and to study
statistical properties of the quantum state. This reproduces aspects of the
West Coast model of 2D gravity and the large-c ensemble of 3D gravity,
including a Page curve, in a higher-dimensional context with generic matter
fields.

High Energy Physics - Theory