"Filtering" CFTs at large N: Euclidean Wormholes, Closed Universes, and Black Hole Interiors

We argue that Euclidean wormhole configurations in AdS/CFT--central to the factorization problem--originate from the erratic $N$-dependence that arises in the large-$N$ limit of conformal field theories (CFTs). We propose that constructing the gravitational dual of a large-$N$ CFT in the semiclassical limit requires a filtering procedure that smooths out this erratic $N$-dependence. Euclidean wormholes--both the external ones connecting disjoint boundaries and the internal ones corresponding to handles--encode correlations of this erratic behavior in Euclidean partition functions. Moreover, internal wormholes do not appear to induce random couplings in the low-energy effective theory of gravity. 

The Lorentzian manifestations of these erratic-$N$ correlations include the emergence of closed universes, their transitions, and black hole interiors. By relating correlations among the erratic components of certain Euclidean partition functions to transitions among closed universes, we derive an infinite tower of inequalities constraining wormhole actions.

We argue that an AdS spacetime entangled with a baby universe is quantum-volatile, reflecting the underlying erratic behavior at large $N$. Furthermore, local operators in a closed universe and in the interior of a black hole are intrinsically erratic, and the black hole interior is quantum-volatile.