# Department of Mathematics

## Unni Namboodiri Lectures in Geometry and Topology

Unni Namboodiri (1956–1981) was a brilliant student of mathematics at the University of Chicago. He died in an automobile accident in December 1981, just a few days after presenting and defending his doctoral thesis Equivariant vector fields on spheres, written under the direction of J. Peter May. The Unni Namboodiri Lecture Series was established in his memory by his family.

### 2016–2017 LecturesMike Hill (UCLA)

#### Lecture 1

Friday, May 12, 2017, 4:00pm–5:00pm

#### Lecture 2

Monday, May 15, 2017, 4:00pm–5:00pm

#### Lecture 3

Tuesday, May 16, 2017, 4:30pm–5:30pm

### 2015–2016 LecturesYves Benoist (Université Paris-Sud) On spectral gaps in simple Lie groups

#### Lecture 1: Dense subgroups in $$\mathrm{SL}(2,\mathbb{R})$$, with N. de Saxce

Monday, May 16, 2016, 4:00pm–5:00pm in Ryerson 251

Abstract: I will focus on proper Borel measurable dense subgroups of $$\mathrm{SL}(2,\mathbb{R})$$ and explain that their Hausdorff dimension is zero. I will also explain why the convolution of sufficiently many compactly supported continuous functions is differentiable. We will see how these two questions are related. The main tool will be a local spectral gap property.

#### Lecture 2: Random walk on $$\mathrm{SL}(2,\mathbb{R})$$, with JF. Quint

Tuesday, May 17, 2016, 4:30pm–5:30pm in Eckhart 202

Abstract: I will focus on random walks on $$\mathrm{SL}(2,\mathbb{R})$$ and explain the law of large numbers for the coefficients. I will also focus on the regularity of the stationary measure on the projective line. We will see how these two questions are related. The main tool will be a spectral gap property.

#### Lecture 3: Tempered homogeneous spaces, with T. Kobayashi

Thursday, May 19, 2016, 4:30pm–5:30pm in Eckhart 202

Abstract: I will focus on unitary representations of $$\mathrm{SL}(n,\mathbb{R})$$ and give a criterion for the temperedness of the regular representations on its algebraic homogeneous spaces. I will also explain the relation between temperedness and induction. We will see how these two questions are related. The main tool will be a uniform spectral gap property.

Past Namboodiri Lecturers include: J. Frank Adams, William Thurston, Shing-Tung Yau, Daniel Quillen, Robert MacPherson, Simon K. Donaldson, Edward Witten, Mikhael Gromov, Gregory A. Margulis, Graeme Segal, Andrew J. Casson, Julius Shaneson, Nigel Hitchin, Dusa McDuff, Clifford Taubes, Alain Connes, Ib Madsen, Michael Hopkins, Yakov Eliashberg, David Gabai, Curt McMullen, Gang Tian, Michael Weiss, John Baez, Étienne Ghys, Nigel Higson, Mladen Bestvina, Douglas C. Ravenel, Danny Calegari, and Larry Guth.