Abstract
Starting with an SO(2)–principal fibration over a closed oriented surface Fg , g ≥ 1, a 2–fold covering of the total space is said to be special when the monodromy sends the fiber SO(2) ∼ S1 to the nontrivial element of Z2 . Adapting D Johnson’s method [11], we define an action of Sp(Z2, 2g), the group of symplectic isomorphisms of (H1(Fg; Z2), .), on the… (More)