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arXiv:2206.13417 · Physical review. D/Physical review. D.

Entanglement wedge cross section inequalities in AdS/BCFT

Pan Li, Yi Ling

Published Oct 27, 2022• 2 citations
arXivHTMLPDF

Abstract

The entanglement wedge cross section in holographic picture provides a geometrical description of the entanglement for mixed states. In this paper we study the inequalities for the entanglement wedge cross section in AdS/BCFT duality. In the presence of the boundary in conformal field theory (CFT), the dual entanglement wedge cross section exhibits abundant phase structures since the extremal surface may end on the brane. We present a universal treatment which is applicable for all the possible phases such that the inequalities for the entanglement wedge cross section can be proved in an algebraic manner rather than a diagrammatic manner. We show that the entanglement wedge cross section in AdS/BCFT satisfies the same inequalities as in AdS/CFT.

DOI
10.1103/physrevd.106.086021

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The entanglement wedge cross section in holographic picture provides a geometrical description of the entanglement for mixed states. In this paper we study the inequalities for the entanglement wedge cross section in AdS/BCFT duality. In the presence of the boundary in conformal field theory (CFT), the dual entanglement wedge cross section exhibits abundant phase structures since the extremal surface may end on the brane. We present a universal treatment which is applicable for all the possible phases such that the inequalities for the entanglement wedge cross section can be proved in an algebraic manner rather than a diagrammatic manner. We show that the entanglement wedge cross section in AdS/BCFT satisfies the same inequalities as in AdS/CFT.
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 AiA_iAi​ the EWP is defined as the region external to all the individual homology regions rAir_{A_i}rAi​​ which consists of the intersection of the entanglement wedge EW(AiA_iAi​) with the time slice. In vacuum AdS3_33​ and BTZ spacetime, 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 AdSd+1_{d+1}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.
A bstract We explore constraints that arise from associating an entanglement wedge (EW) to subregions of a cutoff boundary at a finite distance in AdS/CFT, using a subcritical end-of-the-world (ETW) brane acting as a cutoff. In particular, we consider the case of two intervals in the holographic dual to a BCFT, with one interval A located at the asymptotic boundary and the second interval B located on the ETW brane. We discuss in detail subtleties that arise near the RT end-points when defining the EW for this configuration, particularly in the connected phase. Entanglement wedge nesting (EWN) requires that WE(A) {\mathcal{W}}_E(A) WE​(A) W E A ∪ WE(B) {\mathcal{W}}_E(B) WE​(B) W E B ⊆ WE(A∪B) {\mathcal{W}}_E\left(A\cup B\right) WE​(A∪B) W E A ∪ B . We demonstrate that already in the simplest example of an AdS 3 bulk geometry, EWN can be violated even if A and B are spacelike separated through the bulk and instead we must require the stronger condition that WE(A) {\mathcal{W}}_E(A) WE​(A) W E A be spacelike separated from WE(B) {\mathcal{W}}_E(B) WE​(B) W E B , which highlights the non-local nature of the cutoff theory. Our prescription to associate EWs to subregions on the ETW brane is different from the restricted maximin procedure [1] but will agree within the subset of parameter space where EWN is respected. Additionally, we study EWN in a two sided BTZ black hole geometry with an ETW brane in one of the exteriors. In the BTZ black hole example we find that our condition for EWN disallows configurations where the RT surface goes from the brane to the black hole singularity.
A bstract We study the holographic duality between the reflected entropy and the entanglement wedge cross section with the first order correction. In the field theory side, we consider the reflected entropy for ρABm {\rho}_{AB}^m ρABm​ ρ AB m , where ρ AB is the reduced density matrix for two intervals in the ground state. The reflected entropy in the 2d holographic conformal field theories is computed perturbatively up to the first order in m − 1 by using the semiclassical conformal block. In the gravity side, we compute the entanglement wedge cross section in the backreacted geometry by cosmic branes with tension T m which are anchored at the AdS boundary. Comparing both results we find a perfect agreement, showing the duality works with the first order correction in m − 1.
We establish a construction for the entanglement wedge in asymptotically flat bulk geometries for subsystems in dual (1+1)-dimensional Galilean conformal field theories in the context of flat space holography. In this connection we propose a definition for the bulk entanglement wedge cross section for bipartite states of such dual non relativistic conformal field theories. Utilizing our construction for the entanglement wedge cross section we compute the entanglement negativity for such bipartite states through the generalization of an earlier proposal, in the context of the usual AdS/CFT scenario, to flat space holography. The entanglement negativity obtained from our construction exactly reproduces earlier holographic results and match with the corresponding field theory replica technique results in the large central charge limit.
Abstract We present a new method of deriving shapes of entanglement wedges directly from conformal field theory (CFT) calculations. We point out that a reduced density matrix in holographic CFTs possesses a sharp wedge structure such that inside the wedge we can distinguish two local excitations, while outside we cannot. We can determine this wedge, which we call a CFT wedge, by computing a distinguishability measure. We find that CFT wedges defined by the fidelity or Bures distance as a distinguishability measure coincide perfectly with shadows of entanglement wedges in anti-de Sitter (AdS)/CFT. We confirm this agreement between CFT wedges and entanglement wedges for two-dimensional holographic CFTs where the subsystem is chosen to be an interval or double intervals, as well as higher-dimensional CFTs with a round ball subsystem. On the other hand, if we consider a free scalar CFT, we find that there are no sharp CFT wedges. This shows that sharp entanglement wedges emerge only for holographic CFTs owing to the large-NNN factorization. We also generalize our analysis to a time-dependent example and to a holographic boundary conformal field theory (AdS/BCFT). Finally, we study other distinguishability measures to define CFT wedges. We observe that some of the measures lead to CFT wedges which slightly deviate from the entanglement wedges in AdS/CFT, and we give a heuristic explanation for this. This paper is an extended version of our earlier letter (arXiv:1908.09939 [hep-th]) and includes various new observations and examples.
In this study, we calculate the m − 1 correction to the reflected entropy for two adjacent intervals on a half-infinite line within the AdS 3 / BCFT 2 framework, where m is a Renyi index for a canonical purification. We utilize the doubling trick and compute the leading terms in the large central charge expansion of correlation functions in the holographic boundary conformal field theory (BCFT). In the corresponding anti–de Sitter (AdS) space with an end of the world brane, we analyze the entanglement wedge cross section, the dual counterpart of reflected entropy. This AdS/BCFT setup allows us to explore a richer set of phases in the entanglement wedge cross section. The m − 1 correction in the holographic BCFT manifests as modifications in the entanglement wedge cross section induced by cosmic branes. For the adjacent intervals anchored to the boundary of BCFT, we show the duality between the entanglement wedge cross section with the backreaction from a cosmic brane and Renyi reflected entropy at all orders in m − 1 . Furthermore, by analyzing the entanglement wedge cross section for general adjacent intervals, we provide guidance for an ε expansion of five-point functions in the holographic conformal field theory (CFT), where ε is the rescaled conformal dimension by the central charge.