Local Langlands correspondence for the twisted exterior and symmetric square $\epsilon$-factors of $\textrm{GL}_n$

TL;DR

This paper extends the local Langlands correspondence by defining and proving the equality of twisted symmetric and exterior square L- and epsilon-factors for $ extrm{GL}_n$, using GSpin groups and stability analysis.

Contribution

It introduces twisted symmetric and exterior square L- and epsilon-factors via GSpin groups and proves their equality, advancing the understanding of local Langlands correspondence for these cases.

Findings

Defined twisted symmetric and exterior square L- and gamma-factors.

Established the equality of these twisted factors.

Proved stability of gamma-factors for supercuspidal representations.

Abstract

Let $F$ be a non-Archimedean local field. Let $\mathcal{A}_n(F)$ be the set of equivalence classes of irreducible admissible representations of $\textrm{GL}_n(F)$, and $\mathcal{G}_n(F)$ be the set of equivalence classes of n-dimensional Frobenius semisimple Weil-Deligne representations of $W'_F$. The local Langlands correspondence(LLC) establishes the reciprocity maps $\textrm{Rec}_{n,F}: \mathcal{A}_n(F)\longrightarrow \mathcal{G}_n(F)$ , satisfying some nice properties. An important invariant under this correspondence is the L- and $\epsilon$-factors. This is also expected to be true under parallel compositions with a complex analytic representations of $\textrm{GL}_n(\mathbb{C})$. J.W. Cogdell, F. Shahidi, and T.-L. Tsai proved the equality of the symmetric and exterior square L- and $\epsilon$-factors [7] in 2017. But the twisted symmetric and exterior square L- and $\epsilon$-factor are new and very different from the untwisted case. In this paper we will define the twisted symmetric square L- and $\gamma$-factors using $\textrm{GSpin}_{2n+1}$, and establish the equality of the corresponding L- and $\epsilon$-factors. We will first reduce the problem to the analytic stability of their $\gamma$-factors for supercuspidal representations, then prove the supercuspidal stability by establishing general asymptotic expansions of partial Bessel function following the ideas in [7].