Quantum corrections to entanglement entropy after local quenches in AdS3/CFT2

We compute the leading 1/N corrections to entanglement entropy after a local quench created by a light primary operator of dimension ∆, both in the language of large-c CFTs and in its gravitational dual. The bulk picture of the quench corresponds to a one-particle excited state of a scalar field theory coupled to gravity. The state is fully time-dependent: the particle is initially created at (or close to) the boundary of AdS and then falls into the deep IR, backreacting the geometry as its wavefunction evolves in time. According to the FLM prescription, the entanglement entropy at O(1) receives two contributions: one due to the change in the area in the backreacted geometry, and another one due to bulk entanglement entropy. We compute both contributions and find an exact match with the CFT calculation, providing a non-trivial check of the FLM formula in a dynamic setting. As a byproduct, we show that the contribution from bulk entanglement entropy follows a “Page curve” reminiscent of a black hole evaporation process. We explain the sense in which our calculation can indeed be interpreted as such (i.e. as a toy model for black hole evaporation), and comment on the implications for the information paradox.