Speaker: 

Shahar Mendelson

Institution: 

Australian National University

Time: 

Wednesday, October 4, 2023 - 2:00pm to 3:00pm

Host: 

Location: 

510R Rowland Hall

Consider an isotropic measure μ on Rd (i.e., centered and whose covariance is the identity) and let X1,...,Xm be independent, selected according to μ. If Γ is the random operator whose rows are Xi/m, how does the image of the unit sphere under Γ typically look like? For example, if the extremal singular values of Γ are close to 1, then this random set is "well approximated" by a d-dimensional sphere, and vice-versa. But is it possible to give a more accurate description of that set? I will show that under minimal assumptions on μ, with high probability and uniformly in a unit vector t, each vector Γt inherits the structure of the one-dimensional marginal X,t in a strong sense. If time permits I will also present a few generalisations of this fact - for an arbitrary indexing set. (A joint work with D. Bartl.)