Functorial transfer for reductive groups and central complexes

A class of Weyl group equivariant $\mathrm{\ell }$-adic complexes on a torus, called the central complexes, was introduced and studied in our previous work on Braverman-Kazhdan conjecture. In this note we show that the category of central complexes admits functorial monoidal transfers with respect to morphisms between the dual groups. Combining with the work of Bezrukavnikov-Deshpande, we show that the $\mathrm{\ell }$-adic bi-Whittaker categories (resp. the category of vanishing complexes, the category of stable complexes) on reductive groups admit functorial transfers. As an application, we give a new geometric proof of Laumon-Letellier’s fromula for transfer maps of stable functions on finite reductive groups.