10,513 research outputs found
The group fixing a completely regular line-oval
We prove that the action of the full collineation group of a symplectic translation plane of even order on the set of completely regular line–ovals is transitive. This provides us with a complete description of the group of collineations fixing a completely regular line–oval
Singer quadrangles
[no abstract available
Two-transitive ovals
An oval script O sign of a projective plane is called two-transitive if there is a collineation group G fixing script O sign and acting 2-transitively on its points. If the plane has odd order, then the plane is desarguesian and the oval is a conic. In the present paper we prove that if a plane has order a power of two and admits a two-transitive oval, then either the plane is desarguesian and the oval is a conic, or the plane is dual to a Lüneburg plane. © de Gruyter 2006
Association schemes from the action of fixing a nonsingular conic in PG(2,q)
The group has an embedding into such that it acts as
the group fixing a nonsingular conic in . This action affords a
coherent configuration on the set of non-tangent lines of the
conic. We show that the relations can be described by using the cross-ratio.
Our results imply that the restrictions and to the sets
of secant lines and to the set of exterior lines,
respectively, are both association schemes; moreover, we show that the elliptic
scheme is pseudocyclic.
We further show that the coherent configuration with even allow
certain fusions. These provide a 4-class fusion of the hyperbolic scheme
, and 3-class fusions and 2-class fusions (strongly regular graphs)
of both schemes and $R_{-}(q^2). The fusion results for the
hyperbolic case are known, but our approach here as well as our results in the
elliptic case are new.Comment: 33 page
Abstract hyperovals, partial geometries, and transitive hyperovals
Includes bibliographical references.2015 Summer.A hyperoval is a (q+2)- arc of a projective plane π, of order q with q even. Let G denote the collineation group of π containing a hyperoval Ω. We say that Ω is transitive if for any pair of points x, y is an element of Ω, there exists a g is an element of G fixing Ω setwise such that xg = y. In1987, Billotti and Korchmaros proved that if 4||G|, then either Ω is the regular hyperoval in PG(2,q) for q=2 or 4 or q = 16 and |G||144. In 2005, Sonnino proved that if |G| = 144, then π is desarguesian and Ω is isomorphic to the Lunelli-Sce hyperoval. For our main result, we show that if G is the collineation group of a projective plane containing a transitivehyperoval with 4 ||G|, then |G| = 144 and Ω is isomorphic to the Lunelli-Sce hyperoval. We also show that if A(X) is an abstract hyperoval of order n ≡ 2(mod 4); then |Aut(A(X))| is odd. If A(X) is an abstract hyperoval of order n such that Aut(A(X)) contains two distinct involutions with |FixX(g)| and |FixX(ƒ)| ≥ 4. Then we show that FixX(g) ≠FixX(ƒ). We also show that there is no hyperoval of order 12 admitting a group whose order is divisible by 11 or 13, by showing that there is no partial geometry pg(6, 10, 5) admitting a group of order 11 or of order 13. Finally, we were able to show that there is no hyperoval in a projective plane of order 12 with a dihedral subgroup of order 14, by showing that that there is no partial geometry pg(7, 12, 6) admitting a dihedral group of order 14. The latter results are achieved by studying abstract hyperovals and their symmetries
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