Geometric constant term functor(s)

Abstract: We study the Eisenstein series and constant term functors in the framework of geometric theory of automorphic functions. Our main result says that for a parabolic P in G with Levi quotient M, the !-constant term functor CT_!:D-mod(Bun_G)-> D-mod(Bun_M) is canonically isomorphic to the -constant term functor CT^-_:D-mod(Bun_G)\to D-mod(Bun_M), taken with respect to the opposite parabolic P^-.