Entangled universes
arXiv:2505.08945 · doi:10.21468/SciPostPhys.19.6.143
Abstract
We propose a generalization of the RT and HRT holographic entanglement entropy formulas to spacetimes with asymptotically Minkowski as well as asymptotically AdS regions. We postulate that such spacetimes represent entangled states in a tensor product of Hilbert spaces, each corresponding to one asymptotic region. We show that our conjectured formula has the same general properties and passes the same general tests as the standard HRT formula. We provide further evidence for it by showing that in many cases the Minkowski asymptotic regions can be replaced by AdS ones using a domain wall. We illustrate the use of our formula by calculating entanglement entropies between asymptotic regions in Brill-Lindquist spacetimes, finding phase transitions similar to those known to occur in AdS. We construct networks of universes by gluing together Brill-Lindquist spaces along minimal surfaces. Finally, we discuss a variety of possible extensions and generalizations, including to universes with asymptotically de Sitter regions; in the latter case, we identify an ambiguity in the homology condition, leading to two different versions of the HRT formula which we call ``orthodox'' and ``heterodox'', with different physical interpretations.
53 pages + appendices. Watch a 4-minute video abstract here: https://youtu.be/2g0pyr6ugrc
References in corpus (77)
- Holographic Derivation of Entanglement Entropy from AdS/CFT
- de Sitter Vacua in String Theory
- A Covariant Holographic Entanglement Entropy Proposal
- Cool horizons for entangled black holes
- Generalized gravitational entropy
- Quantum Extremal Surfaces: Holographic Entanglement Entropy beyond the Classical Regime
- Entanglement Renormalization and Holography
- Holographic quantum error-correcting codes: Toy models for the bulk/boundary correspondence
- The entropy of bulk quantum fields and the entanglement wedge of an evaporating black hole
- Bulk Locality and Quantum Error Correction in AdS/CFT
- Reconstruction of Bulk Operators within the Entanglement Wedge in Gauge-Gravity Duality
- Relative entropy equals bulk relative entropy
- Holographic representation of local bulk operators
- Maximin Surfaces, and the Strong Subadditivity of the Covariant Holographic Entanglement Entropy
- The Gravity Dual of a Density Matrix
- De Sitter Space and the Swampland
- The Ryu-Takayanagi Formula from Quantum Error Correction
- Holographic Entanglement of Purification
- The Trouble with de Sitter Space
- The Holographic Entropy Cone
- Entanglement entropy in Galilean conformal field theories and flat holography
- Entanglement of purification: from spin chains to holography
- Surface/State Correspondence as a Generalized Holography
- Entanglement negativity and minimal entanglement wedge cross sections in holographic theories
- On the Existence of Meta-stable Vacua in Klebanov-Strassler
- Black holes and the multiverse
- Islands in cosmology
- Entanglement Wedge Cross Section from the Dual Density Matrix
- Codimension two holography for wedges
- Flat entanglement spectra in fixed-area states of quantum gravity
- Inflation in AdS/CFT
- Entanglement Wedge Reconstruction via Universal Recovery Channels
- Pseudo Entropy in dS/CFT and Time-like Entanglement Entropy
- Multiboundary Wormholes and Holographic Entanglement
- Simple holographic models of black hole evaporation
- Beyond Toy Models: Distilling Tensor Networks in Full AdS/CFT
- Entanglement Wedge Cross Sections Require Tripartite Entanglement
- Coarse Graining Holographic Black Holes
- de Sitter space, extremal surfaces and "time-entanglement"
- Holography and Entanglement in Flat Spacetime
- A World without Pythons would be so Simple
- Bit Threads and Holographic Monogamy
- de Sitter extremal surfaces
- Holo-ween
- Swing surfaces and holographic entanglement beyond AdS/CFT
- Entanglement Wedges for Gravitating Regions
- Finding Pythons in Unexpected Places
- On extremal surfaces and de Sitter entropy
- Comments on Entanglement Entropy in the dS/CFT Correspondence
- AdS plane waves and entanglement entropy
- Covariant bit threads
- Wedge Holography in Flat Space and Celestial Holography
- A new spectral apparent horizon finder for 3D numerical relativity
- What Happens to Apparent Horizons in a Binary Black Hole Merger?
- On de Sitter future-past extremal surfaces and the "entanglement wedge"
- Ultimate fate of apparent horizons during a binary black hole merger II: Horizons weaving back and forth in time
- One-shot holography
- On the reconstruction of Lifshitz spacetimes
- Horizons in a binary black hole merger I: Geometry and area increase
- Algebras and Hilbert spaces from gravitational path integrals: Understanding Ryu-Takayanagi/HRT as entropy without AdS/CFT
- Cobordism Conjecture in AdS
- Time-symmetric initial data for binary black holes in numerical relativity
- Testing holographic entropy inequalities in 2+1 dimensions
- Minimax surfaces and the holographic entropy cone
- Holography and Riemann Surfaces
- Holograms In Our World
- ER for typical EPR
- The entropy of finite gravitating regions
- Geometric Surprises in the Python's Lunch Conjecture
- Ultimate fate of apparent horizons during a binary black hole merger I: Locating and understanding axisymmetric marginally outer trapped surfaces
- Twice Upon a Time: Timelike-Separated Quantum Extremal Surfaces
- Candidate de Sitter Vacua
- Cosmology from random entanglement
- Does connected wedge imply distillable entanglement?
- Inside the Hologram: Reconstructing the bulk observer's experience
- de Sitter space is sometimes not empty
- Black Hole Complementarity and ER/EPR