Finite period vectors and Gauss sums

We study four sums including the Jacquet–Piatetski-Shapiro–Shalika, Flicker, Bump–Friedberg, and Jacquet–Shalika sums associated to irreducible cuspidal representations of general linear groups over finite fields. By computing explicitly, we relate Asai and Bump–Friedberg gamma factors over finite fields to those over nonarchimedean local fields through level zero supercuspidal representation. Via Deligne–Kazhdan close field theory, we prove that exterior square and Bump–Friedberg gamma factors agree with corresponding Artin gamma factors of their associated tamely ramified representations through local Langlands correspondence. We also deduce product formulæ for Asai, Bump–Friedberg, and exterior square gamma factors in terms of Gauss sums. By combining these results, we examine Jacquet–Piatetski-Shapiro–Shalika, Flicker–Rallis, Jacquet–Shalika, and Friedberg–Jacquet periods and vectors and their connections to Rankin–Selberg, Asai, exterior square, and Bump–Friedberg gamma factors, respectively.