Orthogonal representations of random graphs

Seminar: 
Combinatorics Seminar
Event time: 
Monday, October 8, 2018 - 4:00pm
Location: 
LOM 201
Speaker: 
Noga Alon
Speaker affiliation: 
Princeton University
Event description: 

An orthogonal representation of a graph G is an assignment of a unit vector x(v) in the d-dimensional Euclidean space Rd to every vertex v, so that for every two nonadjacent vertices u and v, the corresponding vectors x(u),x(v) are orthogonal.  Let d(G) denote the minimum dimension d for which such a representation exists.  This quantity and its analogs over other fields arise in the study of the Shannon capacity of G and in the investigation of additional problems in Information Theory.  What is the typical value of d(G) for the binomial random graph G=G(n,0.5)?  In recent work with Balla, Gishboliner, Mond and Mousset, we showed that the answer is Θ(n/logn). This settles a question of Knuth.  I will discuss the background of the question and outline the proof.

Research Area(s): 
Special note: 
This is an unusual meeting time