4-Transitivity and 6-figures in some Moufang-Klingenberg planes

In this paper, the Moufang-Klingenberg plane over a local alternative ring R of dual numbers is studied. It is shown that its collineation group is transitive on quadrangles. It is therefore shown that the coordinatization of these Moufang-Klingenberg planes is independent of the choice of the coordinatization quadrangle. Also, the concept of 6-figures is extended to these Moufang-Klingenberg planes and it is shown that any 6-figure corresponds to only one inversible m ∈ R.     

Projectivities in Moufang-Klingenberg planes

Let = = (,,) be a Moufang-Klingenberg plane coordinatized by a local alternative ring R. We define the projectivities of a line g in geometrically as products of perspectivities. It is shown that under certain conditions the group of projectivities of g is generated by the algebraically defined permutations xx+t (tR), xcx (cR a unit), xx ^–.     

Cross-ratios in Moufang-Klingenberg planes

Certain geometric groups operating on a line g in a Moufang-Klingenberg plane. are described algebraically in terms of the underlying alternative ring R. For the case of the dual numbers R=A+A (A alternative field, ²=0) a notion of cross-ratio is introduced on the line. We establish some connections between the geometric groups and the cross-ratio which are well known from classical projective planes.     

Uniqueness of some cyclic projective planes

For n < 41 and for {121, 125, 128, 169, 256, 1024}, every cyclic projective plane of order n is desarguesian.      

A nearfield-free definition of regular Hughes planes and some embeddings of PG(3,q) in Hughes planes of order q 4

We give a nearfield-free definition of some finite and infinite incidence systems by means of half-points and half-lines and show that they are projective planes. We determine a planar ternary ring for these planes and use it to determine the full collineation group and to demonstrate some embeddings of these planes among themselves. We show that these planes include all finite regular Hughes planes and many infinite ones. We also show that PG(3, q) embeds in Hu(q ⁴) (and show infinite versions of this embedding). Dan Hughes 80th Birthday.     

Sharp homogeneity in affine planes,and in some affine generalized polygons

Let G be a collineation group of a generalized (2n + 1 )-gon Γ and let L be a line such that every symmetry σ of any ordinary (2n + 1 )-gon in Γ containing L with σ(L) = L extends uniquely to a collineation in G. We show that Γ is then a Desarguesian projective plane. We also describe the groups G that arise. As a corollary, we treat the analogous problem without the restriction σ(L) = L.     

Projective planes of type I-4

Geometriae Dedicata -     

On the embedding of some linear spaces in finite projective planes

The problem of embedding of linear spaces in finite projective planes has been examined by several authors ([1], [2], [3], [4], [5], [6]). In particular, it has been proved in [1] that a linear space which is the complement of a projective or affine subplane of order m is embeddable in a unique way in a projective plane of order n. In this article, we give a generalization of this result by embedding linear spaces in a finite projective plane of order n, which are complements of certain regularA-affine linear spaces with respect to a finite projective plane.