Lattices in the cohomology of $U(3)$ arithmetic manifolds

Abstract

Under hypotheses required for the Taylor-Wiles method, we prove for forms of $U(3)$ which are compact at infinity that the lattice structure on upper alcove algebraic vectors or on principal series types given by the $\lambda$-isotypic part of completed cohomology is a local invariant of the Galois representation attached to $\lambda$ when this Galois representation is residually irreducible locally at places dividing $p$. As a crucial input, we establish corresponding mod $p$ multiplicity one results. Our main innovation is the combination of integral Hecke theory and the Taylor--Wiles method.

30 pages. Large revision following referee report. To appear in Math. Ann

References in corpus (1)

• Deformation rings and Hecke algebras in the totally real case

Cited by in corpus (1)

• On mod p local-global compatibility for GL_3 in the ordinary case