Global B(G) with adelic coefficients and transfer factors at non-regular elements

Abstract

The goal of this paper is extend Kottwitz's theory of B(G) for global fields. In particular, we show how to extend the definition of "B(G) with adelic coefficients" from tori to all connected reductive groups. As an application, we give an explicit construction of certain transfer factors for non-regular semisimple elements of non-quasisplit groups. This generalizes some results of Kaletha and Taibi. These formulas are used in the stabilization of the cohomology of Shimura and Igusa varieties.