We consider flag-transitive extensions of the dual Petersen graph satisfying one of the following "pathological" properties: (-riLL) there are pairs of collinear points incident to more than one line; ( -TT) there are triples of collinear points not incident to the same plane. We prove that ihere is just one example-satisfying (~LL), with six points and $6 as its au tomorphism group, and there ...

Each of the d-dimensional dual hyperovals Sh m discovered by Yoshiara [20] gives rise, via affine expansion, to a flag-transitive semibiplane A f (Sh m ). We prove that, if m + h = d + 1, then A f (Sh m ) is an elation semibiplane. In the other cases, if d > 2 then A f (Sh m ) is not isomorphic to any of the examples we are aware of, except possibly for certain semibiplanes obtained from Dn -bu...

It is shown that a flag-transitive C3-geometry of finite order (x, y) with x > 2 is either a finite building of type (73 (and hence the classical polar space for a 6-dimensional symplectic space, a 6-dimensional orthogonal space of plus type, a 6or 7-dimensional hermidan space, a 7-dimensional orthogonal space, or an 8-dimensional orthogonal space of minus type) or the sporadic A7 -geometry wit...

We construct two flag-transitive designs with the parameters of the title, and prove that these are the only two examples. One is pointprimitive and related to unitary geometry, while the other is pointimprimitive and constructed from a one-dimensional affine space. This classification may be contrasted with a construction by Mathon and Spence in 1996 of more than 3700 designs with these parame...

Consider a continuous flow of automorphisms of a G-principal bundle which is chain transitive on its compact Hausdorff base. Here G is a connected noncompact semi-simple Lie group with finite center. The finest Morse decomposition of the induced flows on the associated flag bundles were obtained in previous articles. Here we describe the stable sets of these Morse components and, under an addit...

Consider a continuous flow of automorphisms of a G-principal bundle which is chain transitive on its compact Hausdorff base. Here G is a connected noncompact semi-simple Lie group with finite center. The finest Morse decomposition of the induced flows on the associated flag bundles were obtained in previous articles. Here we describe the stable sets of these Morse components and, under an addit...

A decomposition of a graph is a partition of the edge set. One can also look at partitions of the arc set but in this talk we restrict our attention to edges. If each part of the decomposition is a spanning subgraph then we call the decomposition a factorisation and the parts are called factors. Decompositions are especially interesting when the subgraphs induced by each part are pairwise isomo...

Among the compact homogeneous spaces, a very distinguished subclass is formed by the (generalized) real flag manifolds which by definition are the orbits of the isotropy representations of Riemannian symmetric spaces (sorbits). This class contains most compact symmetric spaces (e.g. all hermitian ones), all classical flag manifolds over real, complex and quaternionic vector spaces, all adjoint ...