Bar-Ilan Combinatorics Seminar The next meeting of the seminar will take place, IYH, (when) Sunday, 14 Iyar (May 6), 14:00-15:30 (where) Room 201 (Math & CS Seminar Room), Building 216, Bar-Ilan University (who) Stefan Gyurki (Ben-Gurion University, Beer Sheva, and Slovak University of Technology, Bratislava) (what) Four infinite families of non-Schurian association schemes of order 2p^2 Abstract: Association schemes form one of the traditional areas of investigations in algebraic graph theory. Catalogues of all small association schemes are available from the website of Hanaki and Miyamoto. It is known that all association schemes of order up to 14 are Schurian, that is they are coming from suitable transitive permutation groups in the standard manner. First examples of non-Schurian association schemes exist on 15, 16 and 18 vertices. In particular, there are only two examples of non-Schurian association schemes of order 18. Starting from a successful computer-free interpretation of these two examples, and using extensive computer algebra experimentation in conjunction with further reasoning, we were able to show the existence of at least four infinite families of non-Schurian association schemes of order 2p^2 (for p prime, p>3). In this lecture I will start from a consideration of the two initial examples on 18 points, and describe some auxiliary coherent configurations. Then the four infinite families of association schemes will be presented. We will discuss some of their properties, as well as their links with certain known objects in extremal graph theory. This is joint work with M. Klin. ************************************************************************* You are all invited! Graduate students are especially welcome. Seminar organizer: Ron Adin <radin@math.biu.ac.il> Seminar's homepage: <http://www.math.biu.ac.il/~radin/comsem/comsem.html> ************************************************************************* --------------------------------------------------------- Technion Math Net-2 (TECHMATH2) Editor: Michael Cwikel <techm@math.technion.ac.il> Announcement from: Ron Adin <radin@math.biu.ac.il>