PrerequisiteBasic algebraic topology and number theoryAbstractI will talk about the basics of cohomology of arithmetic groups focusing on Harder's new book. I will start from simplest cases of the group SL_2 over Z (which covers the chapter 2 and 3 of the book of Harder) and try to be as concrete as possible. The goal is to under these cohomology groups from the point of view of geometry and ar...
IntroductionThis course is an introduction to the convergence and collapsing theory of Riemannian manifolds, which is an important tool in Riemannian geometry. We shall introduce the Gromov-Hausdorff distance and study the convergence theory of Riemannian manifolds with respect to this distance. We will discuss the collapsing theory of Riemannian manifolds with bounded sectional curvatures.Lect...