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Abstracts for Low-dimensional topology seminar

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Euler characteristics and 4-manifolds

Posted in
Speaker: 
Ian Hambleton
Zugehörigkeit: 
McMaster University
Datum: 
Don, 23/03/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall
Parent event: 
Low-dimensional topology seminar

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

Posted in
Speaker: 
Seppo Niemi-Colvin
Zugehörigkeit: 
Indiana University
Datum: 
Don, 20/04/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall
Parent event: 
Low-dimensional topology seminar

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

tba -- CANCELLED --

Posted in
Speaker: 
Gordana Matic
Zugehörigkeit: 
UGA
Datum: 
Don, 04/05/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall
Parent event: 
Low-dimensional topology seminar

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

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

Posted in
Speaker: 
Jiajun Yan
Zugehörigkeit: 
University of Virginia
Datum: 
Don, 11/05/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall
Parent event: 
Low-dimensional topology seminar

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

Strongly quasipositive knots are concordant to infinitely many strongly quasipositive knots

Posted in
Speaker: 
Paula Truöl
Zugehörigkeit: 
ETH Zürich
Datum: 
Mit, 17/05/2023 - 16:30 - 17:30
Location: 
MPIM Lecture Hall
Parent event: 
Low-dimensional topology seminar

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

The Nielsen realization for non-spin 4-manifolds

Posted in
Speaker: 
Mihail Arabadji
Zugehörigkeit: 
UMass Amherst/MPIM
Datum: 
Don, 01/06/2023 - 10:30 - 11:30
Location: 
MPIM Lecture Hall
Parent event: 
Low-dimensional topology seminar

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
Zugehörigkeit: 
UGA/MPIM
Datum: 
Don, 01/06/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall
Parent event: 
Low-dimensional topology seminar

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

Posted in
Speaker: 
Fan Ye
Zugehörigkeit: 
Harvard University
Datum: 
Don, 15/06/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall
Parent event: 
Low-dimensional topology seminar

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

Squeezed knots

Posted in
Speaker: 
Andrew Lobb
Zugehörigkeit: 
University of Durham
Datum: 
Don, 06/07/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall
Parent event: 
Low-dimensional topology seminar

(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

Posted in
Speaker: 
Jeff Brock
Zugehörigkeit: 
Yale University
Datum: 
Don, 13/07/2023 - 12:00 - 13:00
Location: 
MPIM Lecture Hall
Parent event: 
Low-dimensional topology seminar

Contact: Aru Ray

 

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