# Equiangular lines and eigenvalue multiplicities

## Location

Math 380-W

Thursday, February 13, 2020 4:30 PM

Yufei Zhao (MIT)

Solving a longstanding problem in discrete geometry, we determine, for each given fixed angle and in all sufficiently large dimensions, the maximum number of lines pairwise separated by the given angle.

A key ingredient is a new result in spectral graph theory: the adjacency matrix of a connected bounded degree graph has sublinear second eigenvalue multiplicity.

Joint work with Zilin Jiang, Jonathan Tidor, Yuan Yao, and Shengtong Zhang (all MIT)

*Note:*This event has changed due to illness.