Holo-ween

TL;DR

This paper demonstrates that by coupling two holographic CFTs at an interface, one can construct states in one CFT whose dual geometries approximate large regions of a spacetime dual to the other CFT, highlighting the universality of interior spacetime features.

Contribution

It introduces a method to generate CFT$_2$ states from CFT$_1$ states via a regularized quench, enabling approximation of large spacetime regions in holographic duals.

Findings

States of CFT$_2$ can approximate large causal patches of dual spacetime M.

Coupling at an interface allows control over the interior geometry of the dual spacetime.

Interior spacetime depends on entanglement structure, not just microscopic details.

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.