We are pleased to have **Professor Yuval Peres**, Theory Group, Microsoft Research, Redmond, as our honored speaker.

**Thursday, October 5, 2017, at 4:30 PM, in Kent 120, 1028 E. 58th Street**

*Reception following the lecture in Jones 111, at 5:30 PM*

"Gravitational Allocation to Uniform Points on the Sphere"

ABSTRACT: Given uniform points on the surface of a two-dimensional sphere, how can we partition the sphere fairly among them? "Fairly" means that each region has the same area. It turns out that if the given points apply a two-dimensional gravity force to the rest of the sphere, then the basins of attraction for the resulting gradient flow yield such a partition-with exactly equal areas, no matter how the points are distributed. (See the cover of the AMS Notices at http://www.ams.org/publications/journals/notices/201705/rnoti-cvr1.pdf.) Our main result is that this partition minimizes, up to a bounded factor, the average distance between points in the same cell. I will also present an application to almost optimal matching of *n* uniform blue points to *n* uniform red points on the sphere, connecting to a classical result of Ajtai, Komlos and Tusnady (Combinatorica 1984).

Joint work with Nina Holden and Alex Zhai.