低次元トポロジーセミナー


2017/12/5(Tue)

10:30--12:00 数学教室 新セミナー室(D505)

Sang-hyun Kim

Seoul National University

Diffeomorphism Groups of One-Manifolds

Let a>=2 be a real number and k = [a]. We denote by Diff^a(I) the group of C^k diffeomorphisms of a closed interval I such that the k--th derivatives are H将モlder--continuous of exponent (a - k). For each real number a>=2, we construct a finitely generated group G < Diff^a(I) such that G admits no injective homomorphisms into Diff^b(I) for any b>a. We also construct a countable simple group with the same property. This is a joint work with Thomas Koberda.