Schedule Feb 11, 2021
Entanglement entropies of equilibrated pure states in quantum many-body systems and replica wormholes
Hong Liu, MIT
Cite as: doi:10.26081/K6DP5C

We develop a general approximation scheme for calculating quantum informational properties of a pure state that has equilibrated in a non-integrable quantum many-body system. For gravity systems, such as those involving black holes, this approximation gives a prescription for calculating entanglement entropies using Euclidean path integrals which is manifestly consistent with unitarity. Applied to recent models of evaporating black holes and eternal black holes coupled to baths, it provides a derivation of replica wormholes, and elucidates their mathematical and physical origins. In particular, it shows that replica wormholes can arise in a system with a fixed Hamiltonian, without the need for ensemble averages.

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