From: Pat.McSwiggen@UC.Edu (Patrick D. McSwiggen) Newsgroups: sci.math.research Subject: Re: diffeomorphism Date: Mon, 28 Oct 1996 14:24:47 -0500 In article <54sln6$bms@mikasa.iol.it>, pcascini@hotmail.com (paolo cascini) wrote: >I'm not English so you have to soory my language... > >can you find two space that are diffeomorph of class Cn for each n, but >that are not diffepmorph of class c-inf. No. See Hirsch, "Differential Topology", p. 50, Th 2.7. If two C^s manifolds are C^1 diffeomorphic, then they are C^s diffeomorphic. Here s can be infinity. The interesting examples come from manifolds that are homeomorphic (only). -- Patrick D. McSwiggen Internet: pat.mcswiggen@uc.edu Department of Mathematics University of Cincinnati