Holo-ween

TL;DR

The work proposes that interfaces between holographic CFTs allow a state of a second CFT to encode large interior regions of a spacetime dual to a first CFT. By constructing a regularized Euclidean quench across a CFT interface, the authors realize states whose gravity duals feature a dynamical brane separating two AdS sectors, yielding a bubble that can reproduce arbitrarily large portions of the original Wheeler-DeWitt patch. The analysis develops a concrete bottom-up AdS/defect model with planar interfaces, derives the domain-wall dynamics, and compares Euclidean actions to determine the dominant geometry, including AdS and AdS-Schwarzschild phases, even for excited states. Extending to multi-interface chains and non-vacuum states, the paper argues that universal entanglement properties largely determine interior bulk physics, suggesting a unified non-perturbative quantum gravity framework across compatible CFTs. These constructions illuminate connections between interface entropy, holographic duals, and ER=EPR-type geometries, and imply that finite bulk regions may be encoded in a wide class of holographic CFTs.

Abstract

We argue that given holographic CFT$_1$ in some state with a dual spacetime geometry M, and given some other holographic CFT$_2$, we can find states of CFT$_2$ whose dual geometries closely approximate arbitrarily large causal patches of M, provided that CFT$_1$ and CFT$_2$ can be non-trivially coupled at an interface. Our CFT$_2$ states are "dressed up as" states of CFT$_1$: they are obtained from the original CFT$_1$ state by a regularized quench operator defined using a Euclidean path-integral with an interface CFT$_1$ CFT$_2$ and CFT$_1$. Our results are consistent with the idea that the precise microscopic degrees of freedom and Hamiltonian of a holographic CFT are only important in fixing the asymptotic behavior of a dual spacetime, while the interior spacetime of a region spacelike separated from a boundary time slice is determined by more universal properties (such as entanglement structure) of the quantum state at this time slice. Our picture requires that low-energy gravitational theories related to CFTs that can be non-trivially coupled at an interface are part of the same non-perturbative theory of quantum gravity.

Figures (16)

• Figure 1: Left: Wheeler-DeWitt patch $M_1^S$ (shaded blue region) of spacetime $M_1$ dual to CFT${}_1$ state $|\Psi_1 \rangle$ defined at boundary time slice $S$. Right: Geometry $M_2$ dual to CFT${}_2$ state $|\Psi_2 \rangle$ includes a region that approximates a large subset of $M_1^S$.
• Figure 2: Gravity interpretation of two holographic CFTs coupled non-trivially at an interface
• Figure 3: Euclidean path integral defining a quench operator $M_{{\cal I},\epsilon}$ mapping states of CFT${}_1$ to states of CFT${}_2$. Here, I represents a non-trivial conformal interface between the CFTs.
• Figure 4: a) CFT path integral geometry for $\langle \Psi_2|...|\Psi_2 \rangle$. b),c) Possible topologies for the interface brane in the dual Euclidean solution (showing vertical cross section). d)$t=0$ slice of c), providing initial data for the time-symmetric Lorentzian geometry dual to $|\Psi_2 \rangle$ in the case when solutions of the type c) have lowest action.
• Figure 5: Gravity dual of an interface CFT in bottom up model with a constant tension-brane. The angles $\theta_1$ and $\theta_2$ in Poincare coordinates are determined by the AdS lengths $L_1$, $L_2$ and the brane tension $\kappa$. These are related to the CFT parameters $c_1$, $c_2$ and $\log g$. The RT surface for a spatial subsystem including points in each CFT within distance $l$ from the interface is shown in blue.