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Further Evidence Against a Semiclassical Baby Universe in AdS/CFT

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arxiv 2504.14586 v1 pith:7BRIB6YK submitted 2025-04-20 hep-th

classification hep-th
keywords babyuniversesemiclassicalwithoutasymptoticallycannotcorrespondencedual
verification ladder T0 review T1 audit T2 compute T3 formal
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We argue that a large class of asymptotically AdS geometries with a semiclassical baby universe cannot be realized within the AdS/CFT correspondence. This in particular resolves a recent puzzle introduced by Antonini and Rath, in which a single CFT state appeared to simultaneously describe an AdS spacetime with a baby universe and one without. We construct a low-energy (and low complexity) boundary operator whose expectation values in the descriptions with and without the baby universe cannot match if the baby universe is semiclassical. This operator conclusively identifies the actual bulk dual: the spacetime without a semiclassical baby universe. This result assumes only that AdS/CFT admits an extrapolate dictionary and an asymptotically isometric encoding of the causal wedge into the dual CFT, without which the correspondence may well be vacuous.

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Cited by 5 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Observer complementarity for black holes and holography

    hep-th 2025-07 conditional novelty 7.0 of 10

    The authors show that the observer rule of Harlow, Usatyuk, and Zhao yields a self-consistent black hole complementarity for both partially and fully evaporated black holes.

  2. The $\alpha$-states of a string worldsheet

    hep-th 2026-07 conditional novelty 6.0 of 10

    The α-states of the Hurwitz worldsheet are symmetric-group characters weighted by the Poissonized Plancherel measure, so string amplitudes are ensemble averages whose weak-coupling limit is Kerov's central limit theorem.

  3. Baby Universes from Thermal Pure States in SYK

    hep-th 2025-11 conditional novelty 6.0 of 10

    A JT-gravity baby universe is constructed with a microscopic dual given by a low-temperature thermal pure state of two coupled SYK models, and its bulk entanglement to the AdS region is O(N) below the phase transition.

  4. The Baby Universe is Fine and the CFT Knows It: On Holography for Closed Universes

    hep-th 2025-07 conditional novelty 5.0 of 10

    A closed universe in AdS/CFT is not ruled out by recent SWAP-test arguments; the one-dimensional Hilbert space seen from the CFT is external indistinguishability, and CFT data can reconstruct the closed universe's geometry.

  5. On tests for baby universes in AdS/CFT

    hep-th 2025-07 conditional novelty 5.0 of 10

    With a post-selected holographic map for the baby universe, the Engelhardt-Gesteau swap test cannot distinguish the two candidate bulk duals.

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