[Binghamton Geometry/Topology Seminar] (no subject)

[Ross Geoghegan]

                   BINGHAMTON GEOMETRY/TOPOLOGY SEMINAR


   Date: Thursday  November 1, 2005

   Time:  2.50 pm

   Place: Library North 2205 followed by coffee/tea in the Anderson
          Reading Room.

   Speaker: Michael McCooey (Franklin and Marshall)

   Title: Concordance of Zp x Zp actions on the four-sphere.

Abstract: 
The classification of Zp x Zp actions on the four-sphere plays a central
role in the more general study of finite group actions on simply-connected
four-manifolds. Orthogonal actions are easy to understand, and form
our starting point. We discuss the extent to which general (locally
linear) actions resemble linear actions, first from the point of view of
homological fixed-point theory, then with some simple constructions of
nonlinear examples, and finally with an application of surgery theory to
classify these actions up to an appropriate notion of concordance. The
only obstruction to concordance turns out to be a codimension two Arf
invariant. We discuss its geometrical meaning, and briefly discuss the
still-open question of its full realizability.


NOTE:  The seminar has a webpage where the semester's program is listed:

http://math.binghamton.edu/MATH/dept/topsem/index.html

It can also be linked from the Department's Home Page.
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