next up previous contents
Next: Coding TheoryInformation Up: Discrete Algebra and Previous: Université Libre de

Universiteit Gent, Departement voor Fundamentele en Computergerichte Wiskunde

Gunther Cornelissen

Study of the divisor of Eisenstein series related to supersingularity. Algebraic relations between torsion points of elliptic curves. Drinfeld modules and the algebraic structure of rings of modular forms.

Frank De Clerck

Constructions and characterizations of finite incidence structures and their adjacency graphs, with the emphasis on (semi)partial geometries and generalized quadrangles. Spreads of (semi)partial geometries. Distance regular graphs. Conical flocks.

Thomas De Smedt

  1. endomorphism rings of Drinfeld-modules over finite fields and their maximality as an order.
  2. Explicit computations of the index of -coverings of the projective line. (Local case, and prime.)

Wim Mielants

Almost highly transitive permutation groups of countable degree.

Leo Storme

In 1995, my research was focussed on flocks and caps in projective spaces, and on the problem of the slopes of the graph of a function defined over a finite field.

Let be a quadratic cone in , q even, with vertex and with base the conic in the plane . A flock of is a set of q planes , , which intersect the set into q disjoint conics.

The problem of classifying all flocks is still open. Different infinite classes and sporadic examples exist.

From February 18 till March 31, 1995, I visited the University of Western Australia (Perth, Australia) to work together with Prof. Dr. T. Penttila.

During this visit, we managed to classify all monomial flocks of . This means that we classified all flocks projectively equivalent to a flock , .

Our results show that the only monomial flocks are:

(1) the linear flock: and with irreducible over ;
(2) the Fisher-Thas-Walker flock: and with q a non-square;
(3) the Payne flock: and with q a non-square.

These results will be published in the article, entitled: Monomial flocks and ovals.

Dr. A. Cossidente (University of Potenza, Italy) and myself looked for infinite classes of caps in projective spaces. We managed to find two infinite classes of - and -caps in . These caps have the properties of being orbits of cyclic groups, and of being contained in the intersection of parabolic quadrics.

The constructed infinite classes were then used to construct infinite classes of -caps contained in the intersection of hyperbolic quadrics in .

These results will be published in: Caps on parabolic and hyperbolic quadrics.

Prof. Dr. A. Blokhuis, Dr. S.M. Ball, Prof. Dr. A. Brouwer (Technical University of Eindhoven), Prof. Dr. T. Szonyi (Eötvös Loránd University, Budapest, Hungary), and myself studied the number of slopes of the graph of a function defined over a finite field.

Let and let be the set of slopes defined by f.

To find information on |D|, consider the set so that |D| is the number of slopes of secants of U, and map to . If F is a subfield of L, then L is a vector space over F, and a subset V of L will be called F-linear if it is mapped in this way to a F-subspace of L.

Then the following result was obtained:

Let be a point set of size q. Let D be the set of slopes of secants of U, and put . Let e (with ) be the largest integer such that each line with slope in D meets U in a multiple of points. Then we have one of the following:

(i)
e=0 and ,
(ii)
e=1, p=2, and ,
(iii)
, e | n, and ,
(iv)
e=n and N = 1.

Moreover, if or and , then U is a -linear subspace, and all possibilities for N can be determined explicitly.

These results will be published in: On the number of slopes of the graph of a function defined on a finite field.

Prof. Dr. J.W.P. Hirschfeld (University of Sussex, England) and myself wrote in 1995 a survey article containing the most important results on arcs, caps, (multiple) blocking sets, -arcs in projective spaces.

The main results on these topics were gathered in a large number of tables to make these results easily accessible to anyone who needs these results.

The article The packing problem in statistics, coding theory, and finite projective spaces, containing these results, has been accepted for publication in the proceedings of the Bose Memorial Conference (Colorado, June 7-11, 1995) (J. Statist. Planning and Inference).

J. A. Thas

  1. Translation generalized quadrangles of order .
  2. Ovoids and spreads of generalized quadrangles and generalized hexagons.
  3. Generalized quadrangles and the Axiom of Veblen.
  4. Embeddings of polar spaces and generalized polygons.

Jan Van Geel

Quadratic forms over function fields and conics. Description of the algebra of Drinfeld modular forms for artithmetic subgroups of the full modular group GL.

Hendrik Van Maldeghem

A characterization result for Moufang polygons: every finite 2-Moufang polygon is a Moufang polygon. An analogue of Baer's theorem for finite generalized polygons. A characterization of the infinite pappian polygons over an algebraically closed field as the Moufang polygons of finite Morley rank. Determination of weak embeddings of singular orthogonal, symplectic and unitary polar spaces of non-singular rank at least three. Characterizations of classes of finite generalized quadrangles by Veblen's axiom. A coherent theory about folding buildings and unfolding apartments. An elementary proof of Ott's result on polarities of finite generalized hexagons. A construction of new ovoids and spreads in the finite generalized hexagon .

Kristel Van Steen

Non-spherical (mainly affine) Tits-buildings of rank 3. By looking at automorphism groups, we give characterizations of some rank 3 affine buildings.

Karim Zahidi

Decision problems in number theory and algebraic geometry.



next up previous contents
Next: Coding TheoryInformation Up: Discrete Algebra and Previous: Université Libre de



Hans Cuypers
Mon Oct 21 14:47:54 MET DST 1996