On gamma factors for representations of finite general linear groups

We use the Langlands–Shahidi method in order to define the Shahidi gamma factor for a pair of irreducible generic representations of ${\mathrm{GL}}_n\left({\mathbb{F}}_q\right)$ and ${\mathrm{GL}}_m\left({\mathbb{F}}_q\right)$. We prove that the Shahidi gamma factor is multiplicative and show that it is related to the Jacquet–Piatetski-Shapiro–Shalika gamma factor. As an application, we prove a converse theorem based on the absolute value of the Shahidi gamma factor, and improve the converse theorem of Nien. As another application, we give explicit formulas for special values of the Bessel function of an irreducible generic representation of ${\mathrm{GL}}_n\left({\mathbb{F}}_q\right)$.