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Abstracts for Low-dimensional topology seminar

Alternatively have a look at the program.

Euler characteristics and 4-manifolds

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Speaker: 
Ian Hambleton
Affiliation: 
McMaster University
Date: 
Thu, 23/03/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall

Contact: Aru Ray (aruray @ mpim-bonn.mpg.de)

We consider the Euler characteristics of closed orientable 2n-manifolds with a given fundamental group G, and highly-connected universal cover. We  strengthen the 4-dimensional Hausmann-Weinberger estimates and extend to higher dimensions.  As an application we obtain new restrictions for non-abelian finite groups arising as fundamental groups of rational homology 4-spheres.

Invariance of Knot Lattice Homotopy

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Speaker: 
Seppo Niemi-Colvin
Affiliation: 
Indiana University
Date: 
Thu, 20/04/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall

Contact: Aru Ray (aruray @ mpim-bonn.mpg.de)

tba -- CANCELLED --

Posted in
Speaker: 
Gordana Matic
Affiliation: 
UGA
Date: 
Thu, 04/05/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall

Contact: Aru Ray (aruray @ mpim-bonn.mpg.de)

A New Gauge-Theoretic Construction of 4-Dimensional Hyperkähler ALE Spaces

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Speaker: 
Jiajun Yan
Affiliation: 
University of Virginia
Date: 
Thu, 11/05/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall

Contact: Aru Ray (aruray @ mpim-bonn.mpg.de)

Strongly quasipositive knots are concordant to infinitely many strongly quasipositive knots

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Speaker: 
Paula Truöl
Affiliation: 
ETH Zürich
Date: 
Wed, 17/05/2023 - 16:30 - 17:30
Location: 
MPIM Lecture Hall

Contact: Aru Ray (aruray @ mpim-bonn.mpg.de)

The Nielsen realization for non-spin 4-manifolds

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Speaker: 
Mihail Arabadji
Affiliation: 
UMass Amherst/MPIM
Date: 
Thu, 01/06/2023 - 10:30 - 11:30
Location: 
MPIM Lecture Hall

Contact: Aru Ray (aruray @ mpim-bonn.mpg.de)

We are going to show that there are many families of non-spin 4–manifolds for which the smooth Nielsen realization problem fails; that is, there are (finite) subgroups of their mapping class groups that cannot be realized by a group of diffeomorphisms. This extends and complements the recent results for spin 4–manifolds. This is joint work with Inanc Baykur.


 

 


 

4-genus bounds from the 10/8+4 theorem

Posted in
Speaker: 
Gordana Matic
Affiliation: 
UGA/MPIM
Date: 
Thu, 01/06/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall

Contact: Aru Ray (aruray @ mpim-bonn.mpg.de)

Donald and Vafaee described a way to use Furuta’s 10/8 theorem to obstruct sliceness in the 4-ball and Linh Truong used a refinement, the 10/8 +4 theorem of Hopkins-Lin-Shi and Hu, to strengthen this sliceness obstruction. We will show how to expand on this technique to obtain lower bounds for four-ball genus and present some calculations for satellite knots. This is joint work in progress with Sashka Kjuchukova and Linh Truong.

SU(2) representations of small Dehn surgeries on knots

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Speaker: 
Fan Ye
Affiliation: 
Harvard University
Date: 
Thu, 15/06/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall

Contact: Aru Ray (aruray @ mpim-bonn.mpg.de)

Squeezed knots

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Speaker: 
Andrew Lobb
Affiliation: 
University of Durham
Date: 
Thu, 06/07/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall

(Joint work with Peter Feller and Lukas Lewark). A knot is called squeezed if it is a slice of a minimal genus, oriented, connected cobordism from a positive to a negative torus knot. Many popular classes of knots are squeezed. At most six knots of ten or fewer crossings are not squeezed. The Lipshitz-Sarkar stable homotopy type for Khovanov homology provides a (surprisingly?) effective means of obstructing knots from being squeezed. I'll explain all this and also advertize a cash prize of 271 swiss francs.

Geometry, topology, and effective rigidity of hyperbolic 3-manifolds

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Speaker: 
Jeff Brock
Affiliation: 
Yale University
Date: 
Thu, 13/07/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall

Contact: Aru Ray

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