Title: Spectral approach to the chromatic number of a simplicial complex

Abstract: In this talk, we'll summarize results obtained in recent years in a pursuit for spectral bounds for the chromatic number of a simplicial complex. As the principal application, we'll show that Ramanujan complexes serve as family of explicitly constructed complexes with large girth and large chromatic number. We'll also present other results, such as a bound on the expansion and a bound on the mixing of a complex, and refer to open questions.

Based on joint work with S.Evra, A.Lubotzky and O.Parzanchevski.

Abstract: In this talk, we'll summarize results obtained in recent years in a pursuit for spectral bounds for the chromatic number of a simplicial complex. As the principal application, we'll show that Ramanujan complexes serve as family of explicitly constructed complexes with large girth and large chromatic number. We'll also present other results, such as a bound on the expansion and a bound on the mixing of a complex, and refer to open questions.

Based on joint work with S.Evra, A.Lubotzky and O.Parzanchevski.

## Date:

Thu, 21/04/2016 - 12:00 to 13:15

## Location:

Manchester Building (room 209), Jerusalem, Israel