p-ADIC FAMILIES OF AUTOMORPHIC FORMS IN THE μ-ORDINARY SETTING

We develop a theory of p-adic automorphic forms on unitary groups that allows p-adic interpolation in families and holds for all primes p that do not ramify in the reflex field E of the associated unitary Shimura variety. If the ordinary locus is nonempty (a condition only met if p splits completely in E), we recover Hida's theory of p-adic automorphic forms, which is defined over the ordinary locus. More generally, we work over the mu-ordinary locus, which is open and dense. By eliminating the splitting condition on p, our framework should allow many results employing Hida's theory to extend to infinitely many more primes. We also provide a construction of p-adic families of automorphic forms that uses differential operators constructed in the paper. Our approach is to adapt the methods of Hida and Katz to the more general mu-ordinary setting, while also building on papers of each author. Along the way, we encounter some unexpected challenges and subtleties that do not arise in the ordinary setting.