Recent progress on the Gan-Gross-Prasad and Ichino-Ikeda conjectures for unitary groups

In the early 2000s Gan, Gross and Prasad made remarkable conjectures relating the non-vanishing of central values of certain Rankin-Selberg L-functions to the non-vanishing of certain explicit integrals of automorphic forms, called 'automorphic periods', on classical groups. They have been subsequently refined by Ichino-Ikeda and Neal Harris into precise conjectural identities relating these two invariants thus generalizing a famous result of Waldspurger for toric periods on GL(2). In the case of unitary groups, those have been established by Wei Zhang under some local restrictions. I will review the current state of the art on this and in particular how certain results in local harmonic analysis allow to remove almost all the local restrictions made by Zhang.