Presented By: Probability and Analysis Seminar - Department of Mathematics
Probability and Analysis Seminar: New lower bounds for sphere packings and independent sets via randomness
Marcus Michelen (UIC)
We construct new lower bounds for sphere packings in high dimensions and for independent sets in graphs with not-too-large co-degrees. For dimension d, this achieves a sphere packing of density (1 + o(1)) d log d / 2^(d+1). In general dimension this provides the first asymptotically growing improvement for sphere packing lower bounds since Rogers' bound of c*d/2^d in 1947. The proof amounts to a random (very dense) discretization together with a new theorem on constructing independent sets on graphs with not-too-large co-degree. Both steps will be discussed and no knowledge of sphere packings will be assumed or required. Central to the analysis is the study of a random process on a graph. This is based on joint work with Marcelo Campos, Matthew Jenssen and Julian Sahasrabudhe.