Geometric constant term functor(s)

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^-.