From: Yuli Rudyak
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
358 Little Hall
PO Box 118105
Gainesville, FL 32611-8105
USA
TEL: (+1) 352-392-0281 ext. 319(office)
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URL: http://www.math.ufl.edu/~rudyak/