Two dimensional quantum quenches and holography

We propose a holographic realization of quantum quenches in two dimensional conformal field theories. In particular, we discuss time evolutions of holographic entanglement entropy in these backgrounds and compare them with CFT results. The key ingredient of the construction is an introduction of a spacetime boundary into bulk geometries, which is the gravity counterpart of a boundary state in the dual CFT. We consider several examples, including local quenches and an inhomogeneous quench which is dual to fusion of two black string into the third one.