On functors associated to a simple root

Associated to a simple root of a finite-dimensional complex semisimple Lie algebra, there are several endofunctors (defined by Arkhipov, Enright, Frenkel, Irving, Jantzen, Joseph, Mathieu, Vogan and Zuckerman) on the BGG category . We study their relations, compute cohomologies of their derived functors and describe the monoid generated by Arkhipovʹs and Josephʹs functors and the monoid generated by Irvingʹs functors. It turns out that the endomorphism rings of all elements in these monoids are isomorphic. We prove that the functors give rise to an action of the singular braid monoid on the bounded derived category of . We also use Arkhipovʹs, Josephʹs and Irvingʹs functors to produce new generalized tilting modules.