University of Manitoba

Wed 29 Mar 2017, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

The spaces of left and circular orderings of a group

ESB 4133 (PIMS Lounge)
Wed 29 Mar 2017, 3:15pm4:15pm
Abstract
A group is leftorderable if it has a strict total ordering that is invariant under multiplication from the left. For countable groups, this is equivalent to acting on the real line by orderpreserving homeomorphisms. A group being circularly orderable has a slightly trickier algebraic definition than leftorderability, but in the countable case boils down, as expected, to the existence of a orientationpreserving action by homeomorphisms on the circle.
The set of all leftorderings of a group forms a topological space, and similarly, so does the set of all circular orderings. I will provide an introduction to these spaces, and discuss recent progress towards understanding the structure of groups whose spaces of circular orderings are “degenerate”, in the sense that they consist simply of a finite set of points with the discrete topology. This is joint work with Cristobal Rivas and Kathryn Mann.
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McMaster University

Wed 5 Apr 2017, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

Group actions on homology 3spheres

ESB 4133 (PIMS Lounge)
Wed 5 Apr 2017, 3:15pm4:15pm
Abstract
I will discuss finite group actions on integral or rational homology 3spheres. The main examples for this talk are the Brieskorn integral homology 3spheres M(p,q,r) arising from isolated singularities, which bound smooth 4manifolds with definite intersection forms. In addition, there are special infinite families of Brieskorn homology 3spheres which can be realized as boundaries of smooth contractible 4manifolds. We ask whether the free periodic actions on Brieskorn spheres extend to smooth actions with isolated fixed points on one of these associated 4manifolds.
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UBC

Wed 12 Apr 2017, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

TBA

ESB 4133 (PIMS Lounge)
Wed 12 Apr 2017, 3:15pm4:15pm
Abstract
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UBC

Wed 19 Apr 2017, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

TBA

ESB 4133 (PIMS Lounge)
Wed 19 Apr 2017, 3:15pm4:15pm
Abstract
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MIT

Wed 3 May 2017, 3:15pm
Topology and related seminars
ESB 4133 (PIMS Lounge)

TBA

ESB 4133 (PIMS Lounge)
Wed 3 May 2017, 3:15pm4:15pm
Abstract
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