Hyperelliptic plane curves of type .
There are several topological spaces associated to a complex hyperplane arrangement: the complement and its boundary manifold, as well as the Milnor fiber and its own boundary. All these spaces are related in various ways, primarily by a set of interlocking fibrations. We use cohomology with coefficients in rank local systems on the complement of the arrangement to gain information on the homology of the other three spaces, and on the monodromy operators of the various fibrations.
We prove that the exceptional complex Lie group has a transitive action on the hyperplane section of the complex Cayley plane . Although the result itself is not new, our proof is elementary and constructive. We use an explicit realization of the vector and spin actions of . Moreover, we identify the stabilizer of the -action as a parabolic subgroup (with Levi factor ) of the complex Lie group . In the real case we obtain an analogous realization of .