Uniqueness of the inversive plane of order 5

It is proved that any inversive plane of order 5 must be isomorphic with the Miquelian plane. The proof is given in some detail: a companion paper will assert that the same arguments can be applied to a plane of order 7.     

Translation planes admitting a pair of index three homology groups

It is shown that a translation plane of order which admits two homology groups of order must in fact admit symmetric homology groups of this order. It is further shown that a plane admitting such symmetric index 3 homology groups is, with a finite number of exceptions, a generalized André plane. A list of the possibly exceptional orders is determined. Received 20 March 2000.     

A characterization of Hering's plane of order 27

Hering's translation plane of order 27 has been characterized by its order and the fact that it admits SL(2, 13) in its translation complement (see [1]). We show that, aside from the Desarguian plane and a Generalized, André plane, it is the only plane of order 27 which admits a subgroup of SL(2, 13) of order 13×12.Partially supported by FONDECYT 0343 and ANDES FOUNDATION.     

A connection between Fano configurations and Minkowski planes of odd order

It is shown in this paper that a pair of points contained in a Fano configuration in a projective plane of odd order cannot induce a Minkowski plane. From this result we derive that no pair of points in the Hughes plane of order 9 can induce a Minkowski plane.     

Subplanes of projective planes of order 121

We determine orbit representatives of all proper subplanes generated by quadrangles of a Veblen-Wedderburn (VW) plane Π of order 11² and the Hughes plane Σ of order 11² under their full collineation groups. In Π, there are 13 orbits of Baer subplanes all of which are desarguesian and approximately 3000 orbits of Fano subplanes. In Σ, there are 8 orbits of Baer subplanes all of which are desarguesian, 2 orbits of subplanes of order 3 and at most 408,075 distinct Fano subplanes. This work was motivated by the well-known question: “Does there exist a non-desarguesian projective plane of prime order?” The question remains unsettled.     

On the automorphism group of inversive planes of odd order

The structure of the fix bundle free automorphism groups of inversive planes of odd order is determined. As a special case of our main result, the automorphism groups with a transitive action on the points of an inversive plane of odd order are essentially determined, and the plane is shown to be miquelian when these have no non-trivial normal subgroups of odd order.     

Nonexistence of certain planes of order 10 and 12

It is shown here that no plane of order 12 exists which has a group of elations of order 12. It is also shown that no plane of order 10 exists which has a multiplicative loop that is a group.     

基于有限射影平面上(ω,r,d)-CFF(N,T)系统的构作

在有限射影平面上利用有限射影平面的性质构作了(ω,r,d)-CFF(N,T)系统,并利用有限射影平面的性质计算了它的参数.最后利用一个有限点集构作了一个(ω,r,d)-DS(N,T)系统并计算了它的参数.     

A partial plane of order 6 constructed from the icosahedron

We show that a maximal partial plane of order 6 with 31 lines and a maximal pure partial plane of order 6 with 25 lines can be constructed from the icosahedron and the Petersen graph. To Daniel R. Hughes, to commemorate his 80th birthday, August 7th, 2007.     

The order of the automorphism group of a binary $${\varvec{}}$$-analog of the Fano plane is at most two

The question if there exists a q-analog of the Fano plane is open since it was first posed in 1972. For a putative binary q-analog of the Fano plane all automorphisms of order greater than 4 had been excluded previously. Here, it is shown with theoretical and computational methods that the order of the automorphism group of a binary q-analog of the Fano plane is either trivial or of order 2. Moreover, some groups which had been excluded by computer search in Braun et al. (Eur J Comb 51:443–457, 2016) are ruled out as automorphism group by theoretic arguments.     

Representations of SL(2,4) on translation planes of even order

A representation for SL(2,4) In characteristic 2 is given which leads to a group theoretic construction of the Dempwolff plane of order 16. Using this construction,it is further shown that the Dempwolff plane may be obtained by the derivation of the semifield plane of order 16 and kern GF(2).     

n阶仿射平面上d-disjunct矩阵的讨论

分组测试的NGT算法在许多领域有着广泛的应用,它的数学模型是d-disjunct矩阵.近年来,人们借助于复形理论、图理论、空间理论和容错估算等来研究它.介绍了分组测试和仿射平面的基本知识,在n阶仿射平面上构作了d-disjunct矩阵,证明了它的一些性质,与n阶射影平面上的d-disjunct矩阵作了比较.     

右半平面上Laplace-Stieltjes变换的值分布

对右半平面上τ(2<τ<+∞)级Laplace-Stieltjes变换,在一定条件下,在虚轴上必有一个涉及小函数关于型函数的Borel点;对右半平面上无穷级Laplace-Stieltjes变换,在一定条件下,在虚轴上必有一个涉及小函数的无穷级Borel点.     

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.     

Collineations of projective planes of order 10, part I

No projective plane of order 10 has a collineation group of order 9 which fixes a 12-arc, a set of twelve points no three collinear, as a set. This fact, proved in Part I, is used to prove in Part II that the full collineation group of any projective plane of order 10 has order 1, 3, or 5.     

On equations of the state of stress in a plate of variable thickness

Method of asymptotic integration of three-dimensional equations of the theory of elasticity is used to construct the internal state of stress in a plate of variable thickness /1/. It is shown that it can generally be described by a system of differential equations of eighth order in the components of the displacement vector of the points of a plane projected inside the plate, with the equations of flexure and of plane state of stress not separated. In a particular case when the face surfaces are symmetrical with respect to this plane, the flexure and the plane state of stress are described by separate equations. The accuracy of the equations obtained is of the order of square of relative thickness of the plate away from the edge and other distortion lines of the stress state.

The boundary layer is not considered and conditions at the plate edge are not formulated.     

On Projective Planes of Order 15 Admitting a Collineation of Order 7

In this article we prove that there is no projective plane of order 15 admitting a collineation group of order 21. C. Y. Ho proved that there is no projective plane of order 15 admitting a collineation group of order 49. But his proof is incorrect. We also correct his error. The conclusion remains the same. We used a computer for our research.     

Some basic properties of planar Singer groups

A planar Singer group is a collineation group of a finite (in this article) projective plane acting regularly on the points of the plane. Theorem 1 gives a characterization of abelian planar Singer groups. This leads to a necessary and sufficient condition for an inner automorphism to be a multiplier. The Sylow 2-structure of a multiplier group and some of its consequences are given in Theorem 3. One important result in studying multipliers of an abelian Singer group is the existence of a common fixed line. We extend this to an arbitrary planar Singer group in Theorem 4. Theorem 5 studies the order of an abelian group of multiplers. If this order equals to the order of the plane plus 1, then the number of points of the plane is a prime. If this order is odd, then it is at most the planar order plus 1.Partially supported by a NSA grant.     

Generic singularities of implicit systems of first order differential equations on the plane

For the implicit systems of first order ordinary differential equations on the plane there is presented the complete local classification of generic singularities of family of its phase curves up to smooth orbital equivalence. Besides the well-known singularities of generic vector fields on the plane and the singularities described by a generic first order implicit differential equations, there exists only one generic singularity described by the implicit first order equation supplied by Whitney umbrella surface generically embedded to the space of directions on the plane.