Universal Properties in ICFTs

Conformal interfaces are not well-studied except for special interfaces called topological interfaces. This lack of study is due to general interfaces breaking symmetry, where some powerful tools in CFT are not applicable. On this background, AdS/CFT can be a powerful tool. In this talk, we make use of AdS/CFT to understand universal properties of conformal interfaces in 2D. Interestingly, we show that the generalized holographic c-theorem can be interpreted as the upper bound on the entanglement between two (possibly different) systems. Moreover, we also show its CFT proof by using the results on the gravity side as a hint. Finally, we give the higher-dimensional generalization of our results. The key is that methods on the gravity side generally do not depend on dimensions, unlike QFT methods. This is another advantage of AdS/CFT to explore quantum many-body systems.