The Entanglement Wedge Polygon
Pith reviewed 2026-06-26 14:03 UTC · model grok-4.3
The pith
The entanglement wedge polygon is a topological quantity in vacuum AdS3 as a consequence of the Gauss-Bonnet theorem.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The entanglement wedge polygon is defined for a pure state and a boundary partition into regions A_i as the region external to all individual homology regions r_{A_i} that consists of the intersection of the entanglement wedges EW(A_i) with the time slice. In vacuum AdS3 this quantity is topological as a direct consequence of the Gauss-Bonnet theorem. In higher dimensions the construction is examined through concrete calculations in vacuum, black brane, and soliton solutions of AdS_{d+1} as well as geometries with end-of-the-world branes.
What carries the argument
The entanglement wedge polygon (EWP), the codimension-1 region external to all individual homology regions r_{A_i} formed by intersecting the entanglement wedges EW(A_i) with the time slice.
If this is right
- The EWP area or invariant remains fixed under continuous deformations of the bulk geometry in vacuum AdS3.
- The construction yields well-defined results in black brane and soliton backgrounds in higher-dimensional AdS.
- The same region can be defined for mixed states by suitable extension of the pure-state prescription.
- The EWP may be connected to existing measures of multi-partite entanglement through its boundary data.
Where Pith is reading between the lines
- If the EWP encodes genuine multi-partite information it could be compared against holographic negativity or other tripartite measures in the same geometries.
- The topological invariance might serve as a diagnostic that distinguishes vacuum states from excited or thermal states where the invariance fails.
- A higher-dimensional analog of the Gauss-Bonnet relation for the EWP, if found, would allow direct computation without explicit minimization.
Load-bearing premise
The proposed definition of the EWP as the region external to all individual homology regions r_Ai and consisting of the intersection of EW(Ai) with the time slice is both well-defined and physically meaningful across the considered geometries and state types.
What would settle it
An explicit computation of the EWP area or associated topological invariant in a continuously deformed vacuum AdS3 geometry that yields a non-constant value would falsify the topological claim.
read the original abstract
In this work we consider a particular codimension-1 region of a holographic spacetime which we call the entanglement wedge polygon (EWP). For a pure state and a partition of the boundary into a number of regions $A_i$ the EWP is defined as the region external to all the individual homology regions $r_{A_i}$ which consists of the intersection of the entanglement wedge EW($A_i$) with the time slice. In vacuum AdS$_3$ the quantity is topological as a direct consequence of the Gauss-Bonnet theorem. In higher dimensions we make progress by considering a number of concrete examples including vacuum, black brane, and soliton solutions of AdS$_{d+1}$ as well as spacetime geometries with end of the world branes dual to boundary conformal field theories. We provide a suitable generalization to mixed states and comment on possible connections between the EWP and measures of multi-partite entanglement.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript introduces the entanglement wedge polygon (EWP) as a codimension-1 region in holographic spacetimes. For a pure state with boundary partitioned into regions A_i, the EWP is defined as the region external to all individual homology regions r_{A_i} and consisting of the intersection of the entanglement wedges EW(A_i) with the time slice. The central claim is that in vacuum AdS_3 this quantity is topological as a direct consequence of the Gauss-Bonnet theorem. The paper examines concrete examples in higher-dimensional AdS solutions (vacuum, black brane, soliton), geometries with end-of-the-world branes, provides a generalization to mixed states, and comments on connections to multi-partite entanglement measures.
Significance. If the EWP definition is unambiguous and the topological property holds, this introduces a new geometric object potentially linking holography to multi-partite entanglement. The concrete examples across geometries and the mixed-state extension provide tangible content, but overall significance depends on whether the construction yields a canonical, well-defined region whose Gauss-Bonnet integral is strictly topological.
major comments (1)
- [Definition of the EWP] Definition of EWP: the construction combines 'external to all r_{A_i}' with 'intersection of EW(A_i) with the time slice'. For n>2 these criteria need not coincide or select a unique component; the intersection may be empty or multiply connected while the complement of the union of r_{A_i} admits multiple regions. Without an explicit rule selecting the intended domain and its boundary, the boundary geodesic-curvature terms in the Gauss-Bonnet formula are not guaranteed to cancel, undermining the claim that the quantity is topological 'as a direct consequence' of the theorem in vacuum AdS_3.
Simulated Author's Rebuttal
We thank the referee for their careful reading and for identifying a potential ambiguity in the definition of the entanglement wedge polygon. We address the major comment below with clarification and a commitment to revision.
read point-by-point responses
-
Referee: Definition of EWP: the construction combines 'external to all r_{A_i}' with 'intersection of EW(A_i) with the time slice'. For n>2 these criteria need not coincide or select a unique component; the intersection may be empty or multiply connected while the complement of the union of r_{A_i} admits multiple regions. Without an explicit rule selecting the intended domain and its boundary, the boundary geodesic-curvature terms in the Gauss-Bonnet formula are not guaranteed to cancel, undermining the claim that the quantity is topological 'as a direct consequence' of the theorem in vacuum AdS_3.
Authors: We agree that the original wording leaves room for ambiguity when n>2. The manuscript defines the EWP as the intersection of the EW(A_i) on the time slice; this intersection lies external to each individual r_{A_i} by construction, since each EW(A_i) is the region on one side of the RT surface homologous to A_i. To remove any ambiguity we will revise the definition to state explicitly that the EWP is the connected component of this intersection that lies in the complement of the union of all r_{A_j}. In vacuum AdS_3 the boundaries of this region consist exclusively of geodesic segments (portions of the RT surfaces). The geodesic curvature therefore vanishes identically along the entire boundary. Gauss-Bonnet then reduces the integral of the Gaussian curvature to 2π times the Euler characteristic of the region, which is a topological invariant. We will add a short paragraph and a three-region example illustrating the selection rule and confirming that the boundary terms cancel, thereby restoring the claim that the quantity is topological as a direct consequence of the theorem for the unambiguously defined region. revision: partial
Circularity Check
No circularity: new definition with independent Gauss-Bonnet application
full rationale
The paper introduces the EWP via an explicit geometric definition (region external to all r_{A_i} as intersection of EW(A_i) with time slice) and then applies the Gauss-Bonnet theorem to vacuum AdS3 to conclude the quantity is topological. This is a direct consequence of the theorem on a well-defined 2D domain and does not reduce to any fitted parameter, self-citation chain, or redefinition of inputs. No load-bearing step equates the claimed topological invariance to the definition by construction. The work examines concrete examples in higher dimensions without circular reductions. This is the normal case of a self-contained definition plus external theorem.
Axiom & Free-Parameter Ledger
axioms (1)
- standard math Gauss-Bonnet theorem applies directly to the EWP in vacuum AdS3
invented entities (1)
-
entanglement wedge polygon
no independent evidence
Reference graph
Works this paper leans on
-
[1]
’t Hooft,Dimensional reduction in quantum gravity,Conf
G. ’t Hooft,Dimensional reduction in quantum gravity,Conf. Proc. C930308(1993) 284 [gr-qc/9310026]
Pith/arXiv arXiv 1993
-
[2]
Susskind,The World as a hologram,J
L. Susskind,The World as a hologram,J. Math. Phys.36(1995) 6377 [hep-th/9409089]
Pith/arXiv arXiv 1995
-
[3]
J. M. Maldacena,The Large N limit of superconformal field theories and supergravity, Adv. Theor. Math. Phys.2(1998) 231 [hep-th/9711200]
Pith/arXiv arXiv 1998
-
[4]
S. S. Gubser, I. R. Klebanov and A. M. Polyakov,Gauge theory correlators from noncritical string theory,Phys. Lett. B428(1998) 105 [hep-th/9802109]. – 66 –
Pith/arXiv arXiv 1998
-
[5]
Witten,Anti-de Sitter space and holography,Adv
E. Witten,Anti-de Sitter space and holography,Adv. Theor. Math. Phys.2(1998) 253 [hep-th/9802150]
Pith/arXiv arXiv 1998
-
[6]
Bombelli, R
L. Bombelli, R. K. Koul, J. Lee and R. D. Sorkin,A Quantum Source of Entropy for Black Holes,Phys. Rev. D34(1986) 373
1986
-
[7]
Srednicki,Entropy and area,Phys
M. Srednicki,Entropy and area,Phys. Rev. Lett.71(1993) 666 [hep-th/9303048]
Pith/arXiv arXiv 1993
-
[8]
C. Holzhey, F. Larsen and F. Wilczek,Geometric and renormalized entropy in conformal field theory,Nucl. Phys. B424(1994) 443 [hep-th/9403108]
Pith/arXiv arXiv 1994
-
[9]
P. Calabrese and J. L. Cardy,Entanglement entropy and quantum field theory,J. Stat. Mech.0406(2004) P06002 [hep-th/0405152]
Pith/arXiv arXiv 2004
-
[10]
S. Ryu and T. Takayanagi,Holographic derivation of entanglement entropy from AdS/CFT,Phys. Rev. Lett.96(2006) 181602 [hep-th/0603001]
Pith/arXiv arXiv 2006
-
[11]
S. Ryu and T. Takayanagi,Aspects of Holographic Entanglement Entropy,JHEP08 (2006) 045 [hep-th/0605073]
Pith/arXiv arXiv 2006
-
[12]
V. E. Hubeny, M. Rangamani and T. Takayanagi,A Covariant holographic entanglement entropy proposal,JHEP07(2007) 062 [0705.0016]
Pith/arXiv arXiv 2007
-
[13]
Swingle,Entanglement Renormalization and Holography,Phys
B. Swingle,Entanglement Renormalization and Holography,Phys. Rev. D86(2012) 065007 [0905.1317]
Pith/arXiv arXiv 2012
-
[14]
F. Pastawski, B. Yoshida, D. Harlow and J. Preskill,Holographic quantum error-correcting codes: Toy models for the bulk/boundary correspondence,JHEP06 (2015) 149 [1503.06237]
Pith/arXiv arXiv 2015
-
[15]
P. Hayden, S. Nezami, X.-L. Qi, N. Thomas, M. Walter and Z. Yang,Holographic duality from random tensor networks,JHEP11(2016) 009 [1601.01694]
Pith/arXiv arXiv 2016
-
[16]
N. Linden, S. Popescu, B. Schumacher and M. Westmoreland,Reversibility of Local Transformations of Multiparticle Entanglement,Quant. Inf. Proc.4(2005) 241 [quant-ph/9912039]
Pith/arXiv arXiv 2005
-
[17]
D¨ ur, G
W. D¨ ur, G. Vidal and J. I. Cirac,Three qubits can be entangled in two inequivalent ways,Phys. Rev. A62(2000) 062314
2000
-
[18]
F. Verstraete, J. Dehaene, B. De Moor and H. Verschelde,Four qubits can be entangled in nine different ways,Phys. Rev. A65(2002) 052112 [quant-ph/0109033]
Pith/arXiv arXiv 2002
- [19]
-
[20]
Horodecki, P
R. Horodecki, P. Horodecki, M. Horodecki and K. Horodecki,Quantum entanglement, Rev. Mod. Phys.81(2009) 865. – 67 –
2009
-
[21]
M. Ma, Y. Li and J. Shang,Multipartite entanglement measures: A review,Fund. Res. 5(2025) 2489 [2309.09459]
arXiv 2025
- [22]
-
[23]
P. Hayden, M. Headrick and A. Maloney,Holographic Mutual Information is Monogamous,Phys. Rev. D87(2013) 046003 [1107.2940]
Pith/arXiv arXiv 2013
-
[24]
T. Takayanagi and K. Umemoto,Entanglement of purification through holographic duality,Nature Phys.14(2018) 573 [1708.09393]
Pith/arXiv arXiv 2018
-
[25]
P. Nguyen, T. Devakul, M. G. Halbasch, M. P. Zaletel and B. Swingle,Entanglement of purification: from spin chains to holography,JHEP01(2018) 098 [1709.07424]
Pith/arXiv arXiv 2018
-
[26]
K. Umemoto and Y. Zhou,Entanglement of Purification for Multipartite States and its Holographic Dual,JHEP10(2018) 152 [1805.02625]
Pith/arXiv arXiv 2018
- [27]
-
[28]
S. Dutta and T. Faulkner,A canonical purification for the entanglement wedge cross-section,JHEP03(2021) 178 [1905.00577]
Pith/arXiv arXiv 2021
- [29]
- [30]
-
[31]
G. Penington, M. Walter and F. Witteveen,Fun with replicas: tripartitions in tensor networks and gravity,JHEP05(2023) 008 [2211.16045]
arXiv 2023
- [32]
- [33]
- [34]
- [35]
-
[36]
B. Liu, J. Zhang, S. Ohyama, Y. Kusuki and S. Ryu,Multiwavefunction overlap and multientropy for topological ground states in (2+1) dimensions,Phys. Rev. B112 (2025) 125160 [2410.08284]. – 68 –
arXiv 2025
- [37]
-
[38]
K. Fujiki and K. Tasuki,Multi-entropy in heavy local quenches,2606.12526
-
[39]
N. Iizuka and M. Nishida,Genuine multientropy and holography,Phys. Rev. D112 (2025) 026011 [2502.07995]
arXiv 2025
- [40]
-
[41]
T. Anegawa, S. Suzuki and K. Tamaoka,Black Holes as a Multipartite Entanglers: Multientropy in AdS3/CFT2,PTEP2026(2026) 043B03 [2512.21037]
arXiv 2026
-
[42]
M. Hu, S. Lin and I. Nechita,Multi-entropy in random tensor networks,2606.04470
-
[43]
N. Bao and I. F. Halpern,Conditional and Multipartite Entanglements of Purification and Holography,Phys. Rev. D99(2019) 046010 [1805.00476]
Pith/arXiv arXiv 2019
-
[44]
M. Headrick, V. E. Hubeny, A. Lawrence and M. Rangamani,Causality & holographic entanglement entropy,JHEP12(2014) 162 [1408.6300]
Pith/arXiv arXiv 2014
-
[45]
A. C. Wall,Maximin Surfaces, and the Strong Subadditivity of the Covariant Holographic Entanglement Entropy,Class. Quant. Grav.31(2014) 225007 [1211.3494]
Pith/arXiv arXiv 2014
-
[46]
B. Czech, J. L. Karczmarek, F. Nogueira and M. Van Raamsdonk,The Gravity Dual of a Density Matrix,Class. Quant. Grav.29(2012) 155009 [1204.1330]
Pith/arXiv arXiv 2012
-
[47]
M. Miyaji and T. Takayanagi,Surface/State Correspondence as a Generalized Holography,PTEP2015(2015) 073B03 [1503.03542]
Pith/arXiv arXiv 2015
-
[48]
P. Caputa, N. Kundu, M. Miyaji, T. Takayanagi and K. Watanabe,Liouville Action as Path-Integral Complexity: From Continuous Tensor Networks to AdS/CFT,JHEP11 (2017) 097 [1706.07056]
Pith/arXiv arXiv 2017
-
[49]
T. Takayanagi,Holographic Spacetimes as Quantum Circuits of Path-Integrations, JHEP12(2018) 048 [1808.09072]
Pith/arXiv arXiv 2018
-
[50]
Susskind,Computational Complexity and Black Hole Horizons,Fortsch
L. Susskind,Computational Complexity and Black Hole Horizons,Fortsch. Phys.64 (2016) 24 [1403.5695]
Pith/arXiv arXiv 2016
-
[51]
D. Stanford and L. Susskind,Complexity and Shock Wave Geometries,Phys. Rev. D 90(2014) 126007 [1406.2678]
Pith/arXiv arXiv 2014
-
[52]
Alishahiha,Holographic Complexity,Phys
M. Alishahiha,Holographic Complexity,Phys. Rev. D92(2015) 126009 [1509.06614]
Pith/arXiv arXiv 2015
-
[53]
O. Ben-Ami and D. Carmi,On Volumes of Subregions in Holography and Complexity, JHEP11(2016) 129 [1609.02514]. – 69 –
Pith/arXiv arXiv 2016
-
[54]
D. Carmi, R. C. Myers and P. Rath,Comments on Holographic Complexity,JHEP03 (2017) 118 [1612.00433]
Pith/arXiv arXiv 2017
-
[55]
R. Abt, J. Erdmenger, H. Hinrichsen, C. M. Melby-Thompson, R. Meyer, C. Northe et al.,Topological Complexity in AdS 3/CFT2,Fortsch. Phys.66(2018) 1800034 [1710.01327]
Pith/arXiv arXiv 2018
-
[56]
R. Abt, J. Erdmenger, M. Gerbershagen, C. M. Melby-Thompson and C. Northe, Holographic Subregion Complexity from Kinematic Space,JHEP01(2019) 012 [1805.10298]
Pith/arXiv arXiv 2019
-
[57]
C. A. Ag´ on, M. Headrick and B. Swingle,Subsystem Complexity and Holography, JHEP02(2019) 145 [1804.01561]
Pith/arXiv arXiv 2019
- [58]
-
[59]
M. Alishahiha, K. Babaei Velni and M. R. Mohammadi Mozaffar,Black hole subregion action and complexity,Phys. Rev. D99(2019) 126016 [1809.06031]
Pith/arXiv arXiv 2019
-
[60]
E. Caceres, S. Chapman, J. D. Couch, J. P. Hernandez, R. C. Myers and S.-M. Ruan, Complexity of Mixed States in QFT and Holography,JHEP03(2020) 012 [1909.10557]
arXiv 2020
-
[61]
W.-C. Gan and F.-W. Shu,Holographic complexity: A tool to probe the property of reduced fidelity susceptibility,Phys. Rev. D96(2017) 026008 [1702.07471]
arXiv 2017
-
[62]
Takayanagi,Holographic Dual of BCFT,Phys
T. Takayanagi,Holographic Dual of BCFT,Phys. Rev. Lett.107(2011) 101602 [1105.5165]
Pith/arXiv arXiv 2011
-
[63]
M. Fujita, T. Takayanagi and E. Tonni,Aspects of AdS/BCFT,JHEP11(2011) 043 [1108.5152]
Pith/arXiv arXiv 2011
-
[64]
Caputa, G
P. Caputa, G. Di Giulio and T. Quang Loc,Complexity inequalities for quantum subsystems, to appear, 2026
2026
-
[65]
Holographic Entanglement Entropy
M. Rangamani and T. Takayanagi,Holographic Entanglement Entropy, vol. 931. Springer, 2017, 10.1007/978-3-319-52573-0, [1609.01287]
work page internal anchor Pith review Pith/arXiv arXiv doi:10.1007/978-3-319-52573-0 2017
-
[66]
V. E. Hubeny, H. Maxfield, M. Rangamani and E. Tonni,Holographic entanglement plateaux,JHEP08(2013) 092 [1306.4004]
Pith/arXiv arXiv 2013
-
[67]
O. Ben-Ami, D. Carmi and J. Sonnenschein,Holographic Entanglement Entropy of Multiple Strips,JHEP11(2014) 144 [1409.6305]
Pith/arXiv arXiv 2014
-
[68]
T. Hartman and J. Maldacena,Time Evolution of Entanglement Entropy from Black Hole Interiors,JHEP05(2013) 014 [1303.1080]. – 70 –
Pith/arXiv arXiv 2013
-
[69]
V. E. Hubeny,Extremal surfaces as bulk probes in AdS/CFT,JHEP07(2012) 093 [1203.1044]
Pith/arXiv arXiv 2012
-
[70]
W. Fischler and S. Kundu,Strongly Coupled Gauge Theories: High and Low Temperature Behavior of Non-local Observables,JHEP05(2013) 098 [1212.2643]
Pith/arXiv arXiv 2013
-
[71]
W. Fischler, A. Kundu and S. Kundu,Holographic Mutual Information at Finite Temperature,Phys. Rev. D87(2013) 126012 [1212.4764]
Pith/arXiv arXiv 2013
-
[72]
Witten,Anti-de Sitter space, thermal phase transition, and confinement in gauge theories,Adv
E. Witten,Anti-de Sitter space, thermal phase transition, and confinement in gauge theories,Adv. Theor. Math. Phys.2(1998) 505 [hep-th/9803131]
Pith/arXiv arXiv 1998
-
[73]
T. Nishioka and T. Takayanagi,AdS Bubbles, Entropy and Closed String Tachyons, JHEP01(2007) 090 [hep-th/0611035]
Pith/arXiv arXiv 2007
-
[74]
I. R. Klebanov, D. Kutasov and A. Murugan,Entanglement as a probe of confinement, Nucl. Phys. B796(2008) 274 [0709.2140]
Pith/arXiv arXiv 2008
-
[75]
P. Calabrese and J. L. Cardy,Evolution of entanglement entropy in one-dimensional systems,J. Stat. Mech.0504(2005) P04010 [cond-mat/0503393]
Pith/arXiv arXiv 2005
-
[76]
J. Haah and D. Stanford,Growth and collapse of subsystem complexity under random unitary circuits,2510.18805
-
[77]
Y. Fan, N. Hunter-Jones, A. Karch and S. Mittal,Sharp Transitions for Subsystem Complexity,2510.18832
-
[78]
D. Carmi, S. Chapman, H. Marrochio, R. C. Myers and S. Sugishita,On the Time Dependence of Holographic Complexity,JHEP11(2017) 188 [1709.10184]
Pith/arXiv arXiv 2017
-
[79]
V. Balasubramanian, A. Bernamonti, J. de Boer, N. Copland, B. Craps, E. Keski-Vakkuri et al.,Holographic Thermalization,Phys. Rev. D84(2011) 026010 [1103.2683]
Pith/arXiv arXiv 2011
-
[80]
B. Chen, W.-M. Li, R.-Q. Yang, C.-Y. Zhang and S.-J. Zhang,Holographic subregion complexity under a thermal quench,JHEP07(2018) 034 [1803.06680]
Pith/arXiv arXiv 2018
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.