Crystalline liftings and the weight part of Serre’s conjecture

We prove some new cases of the weight part of Serre’s conjectures for mod p Galois representation associated to automorphic representations on unitary groups U(d). The approach is a generalization of the work of Gee–Liu–Savitt, namely, we study reductions of certain crystalline representations, as well as crystalline lifts of these reductions.