***********************************
                * Princeton Discrete Math Seminar *
                ***********************************

Date: Thursday 29th September, 3:00 in Fine Hall 224.
 
Speaker: Bhargav Narayanan (Cambridge)

Title - Symmetric intersecting families

A family of sets is said to be intersecting if any two sets in the family 
have nonempty intersection. Families of sets subject to various intersection 
conditions have been studied over the last fifty years and a common feature 
of many of the results in the area is that the extremal families are often 
quite asymmetric. Motivated by this, Peter Frankl conjectured in 1981 that 
symmetric intersecting families must be very small; more precisely, Frankl
conjectured that a family of subsets of {1, 2,..., n}  where any three sets
intersect must have size o(2^n) if its automorphism group is transitive. In
this talk, I shall prove this conjecture.

Based on joint work with David Ellis.

                       -----------

Next week: Celina de Figueiredo

Anyone wishing to be added to or removed from this mailing list should
contact Paul Seymour (pds@math.princeton.edu)