1994 Euler medal awarded to Joseph Thas
From BICA (15) 1995:
The 1994 Euler Medal of the ICA
The Euler Medal of the ICA provides recognition for a distinguished lifetime career contribution to combinatorial research by a Fellow of the ICA who is still active in research. The 1995 Euler Medal has been awarded to Professor Joseph A. Thas of the University of Ghent, Belgium.
Professor Thas has been a Full Professor at the University of Ghent since 1970. He has published 5 books and over 150 papers, is a member of the Belgium Academy of Sciences, Letters, and Fine Arts (since 1988), and serves on the editorial board of various journals. Among other honours he has received the Scientific Louis Empain Award and the Francois Deruyts Award of the Royal Academy of Belgium.
Professor Thas is recognized as one of the world leaders in the field of finite geometry. In his early work, among many original results, he extended the results of Segre on arcs and caps in PG(r,q) to spaces over matrix algebras. Since 1972, he has been heavily involved in the combinatorial study of generalized quadrangles, partial geometries and their generalizations; the book "Finite Generalized Quadrangles" (1984) by S.E. Payne and J.A. Thas is the standard work in the field. Professor Thas has also published widely concerning geometric structures in Galois spaces and the book "General Galois Geometries" (1991) by J.W.P. Hirschfeld and J.A. Thas has been characterized as a monumental achievement of very high quality. His combinatorial research is connected intimately with coding theory, and he has also obtained important results in that area.
A few of Professor Thas's many significant results concerning generalized quadrangles (GQs) include: characterization of the known GQs, work on translation GQs, determination of all GQs that can be embedded in finite affine spaces, study of Moufang conditions for finite GQs, studies of flocks of quadratic cones and the associated translation planes and GQs. His results led to the discovery of the Thas-Fisher GQs and the Fisher-Thas-Walker flocks. He was able to use his results to construct the first non-classical infinite series of perfect codes in distance-regular graphs. He also extended the purely combinatorial results on GQs to partial geometries.
In the field of Galois geometries, he solved Bruck’s "flock conjecture", gave a complete answer to the existence question for proper semi-ovals and semi-ovoids, studied spreads and ovoids of spaces, introduced the technique of derivation of flocks of quadratic cones, classified the flocks of hyperbolic quadrics of PG(3,q), and answered an open problem concerning finite inversive planes of odd order. These are just a few of his diverse contributions to this field of research.
A broadly based researcher in finite geometries, coding theory, generalized quadrangles, and many associated areas, Professor Thas is equally at home in both theoretical and applied combinatorics.