Bar-Ilan Combinatorics Seminar
(joint with the Department of Mathematics Colloquium)
(when)  Sunday, 12 Tevet (Dec. 19), 12:00-13:00      *** NOTE SPECIAL TIME 
(where) Room 201 (Math Department Seminar Room), Math and CS Building
(216), Bar-Ilan University
(who)   Benny Sudakov (UCLA)
(what)  "Expanders, Ramanujan graphs and random lifts"
Expansion of a graph is one of the most fundamental concepts in modern
combinatorics, which has numerous applications in many mathematical
areas. It is well known that expansion is closely relates to the spectral
properties of the graph. The celebrated Alon-Boppana bound says that all
eigenvalues of a d-regular graph must be at least 2sqrt(d-1) - o(1), and
graphs that meet this bound are called Ramanujan Graphs. There are still
many unresolved questions about the existence of such graphs. In this
talk we survey
this background material, and then explain what lifts of graphs are and
how the above questions can be approached using random lifts of graphs.
Joint work with Lubetzky and Vu.
You are all invited! (Graduate students especially welcome)
Seminar organizer: Ron Adin   <> 
Seminar's homepage:   <> 
Technion Math Net-2 (TECHMATH2)
Editor: Michael Cwikel   <> 
Announcement from: Ron Adin   <>