Published online by Cambridge University Press: 12 May 2020
Let $F$ be a
$p$-adic field and choose
$k$ an algebraic closure of
$\mathbb{F}_{\ell }$, with
$\ell$ different from
$p$. We define “nilpotent lifts” of irreducible generic
$k$-representations of
$GL_{n}(F)$, which take coefficients in Artin local
$k$-algebras. We show that an irreducible generic
$\ell$-modular representation
$\unicode[STIX]{x1D70B}$ of
$GL_{n}(F)$ is uniquely determined by its collection of Rankin–Selberg gamma factors
$\unicode[STIX]{x1D6FE}(\unicode[STIX]{x1D70B}\times \widetilde{\unicode[STIX]{x1D70F}},X,\unicode[STIX]{x1D713})$ as
$\widetilde{\unicode[STIX]{x1D70F}}$ varies over nilpotent lifts of irreducible generic
$k$-representations
$\unicode[STIX]{x1D70F}$ of
$GL_{t}(F)$ for
$t=1,\ldots ,\lfloor \frac{n}{2}\rfloor$. This gives a characterization of the mod-
$\ell$ local Langlands correspondence in terms of gamma factors, assuming it can be extended to a surjective local Langlands correspondence on nilpotent lifts.