Entanglement negativity in the multiverse

Understand

We explore quantum entanglement between two causally disconnected regions in the multiverse.

• We first consider a free massive scalar field, and compute the entanglement negativity between two causally separated open charts in de Sitter space.
• The qualitative feature of it turns out to be in agreement with that of the entanglement entropy.
• We then introduce two observers who determine the entanglement between two causally disconnected de Sitter spaces.