researchseminars.org

Linus Hamann (Princeton)
2021-11-04 21:00 - 22:00 UTC | https://researchseminars.org/talk/UCSD_NTS/46/
Title: Compatibility of the Fargues-Scholze and Gan-Takeda local Langlands (https://researchseminars.org/talk/UCSD_NTS/46/)
by Linus Hamann (Princeton) as part of UCSD number theory seminar

Lecture held in APM 6402 and online.

Abstract
Given a prime $p$, a finite extension $L/\mathbb{Q}_{p}$, a connected $p$-adic reductive group $G/L$, and a smooth irreducible representation $\pi$ of $G(L)$, Fargues-Scholze recently attached a semisimple Weil parameter to such $\pi$, giving a general candidate for the local Langlands correspondence. It is natural to ask whether this construction is compatible with known instances of the correspondence after semisimplification. For $G = GL_{n}$ and its inner forms, Fargues-Scholze and Hansen-Kaletha-Weinstein show that the correspondence is compatible with the correspondence of Harris-Taylor/Henniart. We verify a similar compatibility for $G = GSp_{4}$ and its unique non-split inner form $G = GU_{2}(D)$, where $D$ is the quaternion division algebra over $L$, assuming that $L/\mathbb{Q}_{p}$ is unramified and $p > 2$. In this case, the local Langlands correspondence has been constructed by Gan-Takeda and Gan-Tantono. Analogous to the case of $GL_{n}$ and its inner forms, this compatibility is proven by describing the Weil group action on the cohomology of a local Shimura variety associated to $GSp_{4}$, using basic uniformization of abelian type Shimura varieties due to Shen, combined with various global results of Kret-Shin and Sorensen on Galois representations in the cohomology of global Shimura varieties associated to inner forms of $GSp_{4}$ over a totally real field. After showing the parameters are the same, we apply some ideas from the geometry of the Fargues-Scholze construction explored recently by Hansen, to give a more precise description of the cohomology of this local Shimura variety, verifying a strong form of the Kottwitz conjecture in the process.

pre-talk at 1:20pm.

The talk will be given via Zoom, but we will meet in the lecture hall as usual.
