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
(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
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   <> 
Seminar's homepage:
Technion Math Net-2 (TECHMATH2)
Editor: Michael Cwikel   <> 
Announcement from: Ron Adin   <>