# Diffeomorphism Groups of One-Manifolds

2017/12/12 Tue 15:00 - 16:30

6号館609号室

Sang-Hyun Kim

Seoul National University

Let a>=2 be a real number and k = [a]. We denote by Diff^a(S^1) the group of C^k diffeomorphisms such that the k--th derivatives are Hölder--continuous of exponent (a - k). For each real number a>=2, we prove that there exists a finitely generated group G < Diff^a(S^1) such that G admits no injective homomorphisms into Diff^b(S^1) for any b>a. This is joint work with Thomas Koberda.