Types for tame $p$-adic groups


Let $k$ be a non-archimedean local field with residual characteristic $p$. Let $G$ be a connected reductive group over $k$ that splits over a tamely ramified field extension of $k$. Suppose $p$ does not divide the order of the Weyl group of $G$. Then we show that every smooth irreducible complex representation of $G(k)$ contains an $\mathfrak {s}$-type of the form constructed by Kim–Yu and that every irreducible supercuspidal representation arises from Yu’s construction. This improves an earlier result of Kim, which held only in characteristic zero and with a very large and ineffective bound on $p$. By contrast, our bound on $p$ is explicit and tight, and our result holds in positive characteristic as well. Moreover, our approach is more explicit in extracting an input for Yu’s construction from a given representation.


Jessica Fintzen

Trinity College, Cambridge, CB2 1TQ, United Kingdom and Duke University, Durham, NC