# Nonlocal multi-trace sources and bulk entanglement in holographic conformal field theories

## TL;DR

This paper explores how nonlocal multi-trace sources in holographic CFTs influence bulk entanglement and entanglement entropy, showing leading order equivalence to single-trace states and analyzing 1/N corrections with implications for bulk geometry constraints.

## Contribution

It demonstrates that multi-trace sources produce states with similar leading order entanglement entropy as single-trace states and investigates the effects of 1/N corrections on bulk entanglement and geometry.

## Key findings

- Leading order entanglement entropy matches that of single-trace states.
- 1/N corrections exhibit non-analyticity and divergences.
- Bulk entanglement contributions are consistent with quantum corrections to Ryu-Takayanagi formula.

## Abstract

We consider CFT states defined by adding nonlocal multi-trace sources to the Euclidean path integral defining the vacuum state. For holographic theories, we argue that these states correspond to states in the gravitational theory with a good semiclassical description but with a more general structure of bulk entanglement than states defined from single-trace sources. We show that at leading order in large N, the entanglement entropies for any such state are precisely the same as those of another state defined by appropriate single-trace effective sources; thus, if the leading order entanglement entropies are geometrical for the single-trace states of a CFT, they are geometrical for all the multi-trace states as well. Next, we consider the perturbative calculation of 1/N corrections to the CFT entanglement entropies, demonstrating that these show qualitatively different features, including non-analyticity in the sources and/or divergences in the naive perturbative expansion. These features are consistent with the expectation that the 1/N corrections include contributions from bulk entanglement on the gravity side. Finally, we investigate the dynamical constraints on the bulk geometry and the quantum state of the bulk fields which must be satisfied so that the entropies can be reproduced via the quantum-corrected Ryu-Takayanagi formula.