Cosmology from random entanglement

Antonini, Stefano; Sasieta, Martin; Swingle, Brian

doi:10.1007/jhep11(2023)188

J. High Energ. Phys.

2023

DOI: 10.1007/jhep11(2023)188

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Cosmology from random entanglement

Stefano Antonini,

Martin Sasieta,

Brian Swingle

Abstract: We construct entangled microstates of a pair of holographic CFTs whose dual semiclassical description includes big bang-big crunch AdS cosmologies in spaces without boundaries. The cosmology is supported by inhomogeneous heavy matter and it partially purifies the bulk entanglement of two disconnected auxiliary AdS spacetimes. We show that the island formula for the fine grained entropy of one of the CFTs follows from a standard gravitational replica trick calculation. In generic settings, the cosmology is cont… Show more

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2024

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Cited by 10 publications

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“…Explicit examples of such states include the so-called partially entangled thermal states (PETS) in holographic CFTs[35,36,[50][51][52].…”

mentioning

confidence: 99%

Geometric surprises in the Python's lunch conjecture

Arora,

Headrick,

Lawrence

et al. 2024

SciPost Phys.

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A bulge surface, on a time reflection-symmetric Cauchy slice of a holographic spacetime, is a non-minimal extremal surface that occurs between two locally minimal surfaces homologous to a given boundary region. According to the python’s lunch conjecture of Brown et al., the bulge’s area controls the complexity of bulk reconstruction, in the sense of the amount of post-selection that needs to be overcome for the reconstruction of the entanglement wedge beyond the outermost extremal surface. We study the geometry of bulges in a variety of classical spacetimes, and discover a number of surprising features that distinguish them from more familiar extremal surfaces such as Ryu-Takayanagi surfaces: they spontaneously break spatial isometries, both continuous and discrete; they are sensitive to the choice of boundary infrared regulator; they can self-intersect; and they probe entanglement shadows, orbifold singularities, and compact spaces such as the sphere in AdS_p× S^qp×Sq. These features imply, according to the python’s lunch conjecture, novel qualitative differences between complexity and entanglement in the holographic context. We also find, surprisingly, that extended black brane interiors have a non-extensive complexity; similarly, for multi-boundary wormhole states, the complexity pleateaus after a certain number of boundaries have been included.

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“…Explicit examples of such states include the so-called partially entangled thermal states (PETS) in holographic CFTs[35,36,[50][51][52].…”

mentioning

confidence: 99%

Geometric surprises in the Python's lunch conjecture

Arora,

Headrick,

Lawrence

et al. 2024

SciPost Phys.

Self Cite

View full text Add to dashboard Cite

show abstract

A principle of maximum ignorance for semiclassical gravity

de Boer,

Liska,

Post

et al. 2024

J. High Energ. Phys.

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The principle of maximum ignorance posits that the coarse-grained description of a system is maximally agnostic about its underlying microscopic structure. We briefly review this principle for random matrix theory and for the eigenstate thermalization hypothesis. We then apply this principle in holography to construct ensembles of random mixed states. This leads to an ensemble of microstates which models our microscopic ignorance, and which on average reproduces the effective semiclassical physics of a given bulk state. We call this ensemble the state-averaging ansatz. The output of our model is a prediction for semiclassical contributions to variances and higher statistical moments over the ensemble of microstates. The statistical moments provide coarse-grained — yet gravitationally non-perturbative — information about the microstructure of the individual states of the ensemble. We show that these contributions exactly match the on-shell action of known wormhole configurations of the gravitational path integral. These results strengthen the view that wormholes simply parametrize the ignorance of the microstructure of a fundamental state, given a fixed semiclassical bulk description.

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De Sitter space is sometimes not empty

Balasubramanian,

Nomura,

Ugajin

2024

J. High Energ. Phys.

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Multiple lines of evidence suggest that the Hilbert space of an isolated de Sitter universe is one dimensional but can appear larger when probed by a gravitating observer. To test this idea, we compute the von Neumann entropy of a field theory in a two-dimensional de Sitter universe which is entangled in a thermal-like state with the same field theory on a disjoint, asymptotically anti-de Sitter (AdS) black hole. Previously, it was shown that the replica trick for computing the entropy of such entangled gravitating systems requires the inclusion of a non-perturbative effect in quantum gravity — novel wormholes connecting the two spaces. Here we show that: (a) the expected wormholes connecting de Sitter and AdS universes exist, avoiding a no-go theorem via the presence of sources on the AdS boundary; (b) the entanglement entropy vanishes if the nominal entropy of the de Sitter cosmological horizon $$ \left({S}_{\textrm{dS}}={A}_{\textrm{horizon}}^{\textrm{dS}}/4{G}_{\textrm{N}}\right) $$ S dS = A horizon dS / 4 G N is less than the entropy of the AdS black hole horizon $$ \left({S}_{\textrm{BH}}={A}_{\textrm{horizon}}^{\textrm{AdS}}/4{G}_{\textrm{N}}\right) $$ S BH = A horizon AdS / 4 G N , i.e., SdS< SBH; (c) the entanglement entropy is finite when SdS > SBH. Thus, the de Sitter Hilbert space is effectively nontrivial only when SdS > SBH. The AdS black hole we introduce can be regarded as an “observer” for de Sitter space. In this sense, our result is a non-perturbative generalization of the recent perturbative argument that the algebra of observables on the de Sitter static patch becomes nontrivial in the presence of an observer.

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Cosmology from random entanglement

Cited by 10 publications

References 104 publications

Geometric surprises in the Python's lunch conjecture

Geometric surprises in the Python's lunch conjecture

A principle of maximum ignorance for semiclassical gravity

De Sitter space is sometimes not empty

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