Lecture 18: Introduction to Islands
We completed our discussion of simple entanglement wedges in AdS/CFT. We reviewed the replica trick for computing the entanglement entropy and indicated how it can be used to obtain the holographic prescription for entanglement entropy. We then reviewed the setup, where a holographic theory is coupled to a nongravitational bath, that has been used in recent analyses of the Page curve. We wrote down the "island formula" for the entanglement entropy of a part of the nongravitational bath and briefly sketched how the formula leads to a Page curve.
