From: Yuli Rudyak <rudyak@math.ufl.edu>
Date: Wed, 28 Mar 2007 22:49:15 -0400 (EDT)

I have a question for the list

There is a well-known exact sequence
$\pi_0(Diff^+D^n) \to \pi_0(Diff^+S^{n-1}) \to \Gamma_n \to 0$
where $\Gamma_n$ is the group of twisted $n$-spheres and Diff^+ denotes 
the 
group of orientation-preserving diffeomorphisms.

Question: Does somebody know the values (or a value) of $n$ such that the 
first 
map is non-zero. In other words, are there self-diffeomorphisms of a 
sphere that 
extends to the disk but are not isotopic to the identity? 

Yuli

Dr. Yuli B. Rudyak
Department of Mathematics
University of Florida
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URL: http://www.math.ufl.edu/~rudyak/