Combinatorics Seminar - Geunho Lim (University of California, Santa Barbara)

16:15-18:00

Speaker: Geunho Lim (University of California, Santa Barbara)

Title: Bounds on rho-invariants and simplicial complexity of triangulated manifolds

Abstract: In this talk, we show the existence of linear bounds on various rho-invariants. In particular, we construct a desired cobordism over a group, whose complexity is linearly bounded by that of its boundary. Employing a combinatorial concept of G-colored polyhedra, we give linear bounds on Atiyah-Singer invariants of PL manifolds. Using relative hyperbolization, we obtain linear bounds on Cheeger-Gromov invariants of PL manifolds endowed with a faithful representation. As applications, we give concrete examples in the complexity theory of high-dimensional (homotopy) lens spaces. This is a joint work with Shmuel Weinberger.