Arithmetic theta lifts and the arithmetic gan-gross-prasad conjecture for unitary groups

We propose a precise formula relating the height of certain diagonal cycles on the product of unitary Shimura varieties and the central derivative of some tensor product L-functions. This can be viewed as a refinement of the arithmetic Gan-Gross-Prasad conjecture. We use the theory of arithmetic theta lifts to prove some endoscopic cases of it for U(2) × U(3).