Explicit local multiplicative convolution of ℓ-adic sheaves

Abstract

We give explicit formulas for the local multiplicative convolution functors, which express the local monodromies of the convolution of two ℓ-adic sheaves on the torus Gm over the algebraic closure of a finite field in terms of the local monodromies of the factors. As a particular case, we recover Fu’s formulas for the local Fourier transform.