# Towards Spacetime Entanglement Entropy for Interacting Theories (19frg247)

## Organizers

(University of Alberta)

(Perimeter Institute for Theoretical Physics)

In quantum theory it is possible to establish correlations between different regions of spacetime that are stronger than anything achievable in pre-quantum physics. These correlations exist because of a particularly counter-intuitive feature of the theory, namely, entanglement. Entanglement entropy is a standard measure that quantifies the strength of the correlations due to quantum entanglement. However, although this quantity is quite commonly used in the context of quantum systems restricted to spatial regions, it is particularly tricky to calculate it in the problems that arise in quantum gravity which require "spacetime" regions. Progress made in the past for the case of relatively simple non-interacting theories (called gaussian theories") provides clues on how to extend such methods for calculating the spacetime entanglement entropy to the case of interacting theories. Our project seeks to advance this frontier by providing a formulation of spacetime entanglement entropy that applies to a large class of interacting theories that are conformal field theories. This will open up the study of various problems in quantum gravity and cosmology -- such as the microscopic origin of black hole entropy -- enabled by our proposed research.