AUTOMORPHISMS OF BRAID GROUPS ON S2, T2, P2 AND THE KLEIN BOTTLE K
Abstract
It is shown that for the braid group Bn(M) on a closed surface M of nonnegative Euler characteristic, Out(Bn(M)) is isomorphic to a group extension of the group of central automorphisms of Bn(M) by the extended mapping class group of M, with an explicit and complete description of Aut(Bn(S2)), Aut(Bn(P2)), Out(Bn(S2)) and Out(Bn(P2)).