报告题目：Entanglement between two disjoint universes

报告人： Tomonori UGAJIN

报告时间：2020年12月11日（星期五）14：00（北京时间）

报告地点：中心校区物理楼302，在线报告（ZOOM ID： 862 0074 2474  Passcode: 987573）

报告摘要：We use the replica method to compute the entanglement entropy of a universe without gravity entangled in a thermofield-double-like state with a disjoint gravitating universe. Including wormholes between replicas of the latter gives an entropy functional which includes an "island" on the gravitating universe. We solve the back-reaction equations when the cosmological constant is negative to show that this island coincides with a causal shadow region that is created by the entanglement in the gravitating geometry. At high entanglement temperatures, the island contribution to the entropy functional leads to a bound on entanglement entropy, analogous to the Page behavior of evaporating black holes. We also apply the formalism to black holes in de Sitter space, and find similar islands.In every case, if the parent relativistic theory exhibited conformal invariance, we find an infinitely enhanced Galilean conformal invariance in the non-relativistic case. This leads to suggest that the enhancement of symmetries in the non-relativistic limit is a generic feature of conformal field theories in any dimension.

报告人简介：I have been trying to understand how this emergence of spacetime as well as gravity, happens in holographic principle (especially in AdS/CFT correspondence), which is considered as a way to define a quantum theory of gravity. In doing so, relative entropy, one of the central concepts in quantum information theory, plays a key role. In addition to this, I am also interested in applications of relative entropy to other fields of theoretical physics such as condensed matter theory and non equilibrium physics.　

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