Title: Matrix concentration and sparsification
Speaker: Nick Harvey (University of British Columbia)

Abstract:
In the past 10 years, several research communities have studied problems of the following form: 
Given a matrix A represented as a sum of certain positive semidefinite matrices, we would like to 
approximately represent A as a weighted sum of fewer of those matrices. Spectral sparsification 
of graphs is a special case of this problem.  The problem is also closely related to some concentration 
inequalities for randomly sampling matrices. This talk will survey various results on this topic.