Critical-point unitarizability and Arthur-packet conjecture

Let $\pi$ be an irreducible subquotient at a critical point for a classical group, with no restriction on the rank. Critical-point Arthur-packet conjecture. The following are equivalent: $\pi$ is unitarizable, and $\pi$ belongs to some Arthur packet. The paper proves this equivalence in corank at most $3$; the conjecture extends that result to arbitrary rank.