|講演タイトル||Entanglement between two disjoint universes|
We study island phenomena of a thermo field like entangled state on two disjoint universes when gravity is turned only on one of them.
We show even in this case the entanglement entropy between two universes is computed by a generalized entropy, of the region on the gravitating universe which minimizes the function.
The entanglement between two universes creates a causal shadow region in the black hole in the gravitating universe, which is identified with the island in this set up in the high temperature limit. We also confirm when the entanglement temperature is larger than the temperature of the black hole, the entanglement entropy between two universe coincides with the black hole entropy, a kind of Page behavior.The growth of the causal shadow region in the black hole interior has a natural interpretation in the holographic dual of this setup. The holographic setup involves one dimensional higher eternal black hole, whose boundaries naturally realize two universes. Since the causal shadow defines an interval on one of the boundaries, its growth means the growth of the entanglement wedge of the non gravitating universe, which leads to the complete bulk reconstruction from the non gravitating boundary.