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Cotygodniowe seminarium badawcze
2019-11-13, godz. 16:15, 4070
Andrzej Szczepański (UG)
Spajające grupy Bieberbacha (za Mariusem Dadarlatem)
C* - algebrę A nazywamy spajajacą (connective) o ile istnieje *-monomorfizm z A do pewnej "uniwersalnej" C*-algebry. C* - algebrę grupową C*(G) nazywamy spajajacą o ile jej ideał augumentacji (jadro odwzorowania C*(G) ----> \C) jest C*-algebrą spajajacą (\C-liczby zespolone). By...
2019-11-06, godz. 16:15, 4070
Andrzej Weber (UW)
O ekwiwariantnych eliptycznych kohomologiach
Przypomnę klasyczne eliptyczne kohomologie, tak jak były definiowane w atykule Graema Segala "Elliptic Cohomology" z 1988-go roku i porównam z nowym podejściem opisanym w pracy Nory Ganter "The elliptic Weyl character formula", arXiv:1206.0528. ...
2019-10-30, godz. 16:15, 4070
Jkub Koncki (UW)
Motivic Chern Classes Of Configuration Spaces
We calculate equivariant motivic Chern class for configuration space of smooth variety and space of vectors with different directions. We prove formulas for generating series of these classes. We generalize localization theorems results about BB-decomposition to acquire some stability fo motivic Che...
2019-10-16, godz. 16:15, 4070
Wojciech Politarczyk (UW)
Non-slice linear combinations of iterated torus knots
Algebraic knots are knots which arise as links of isolated singularities of complex curves. Lee Rudolph conjectured that the set of algebraic knots is linearly independent in the smooth knot concordance group. Rudolph’s conjecture is very closely related to one of the most important conjecture...
2019-07-04, godz. 14:15, 3130
Józef Przytycki (George Washington University)
2019-06-11, godz. 16:15, 3180
Łukasz Grabowski (Lancaster University)
Approximation of groups with respect to the rank metric
Abstract: I'll talk about an ongoing joint work with Gabor Elek about approximation of groups with respect to the rank metric. The basic question is the following variant of the Halmos problem about commuting matrices: if A and B are large matrices such that the rank of the image of the commutat...
2019-06-04, godz. 16:15, 3180
Thomas Koberda (University of Virginia)
Algebra versus regularity for group actions on one-manifolds
JOINT WITH SIMONS SEMESTER I will survey some results concerning the algebraic structure of finitely generated groups which admit faithful actions on compact one-manifolds. I will concentrate on continuous, C^1 , and C^2 actions, and on the various algebraic restrictions imposed by regularity requi...
2019-05-28, godz. 16:15, 3180
Genevieve Walsh (Tufts University)
Incoherence of many free by free groups
A group is coherent if every finitely generated subgroup is finitely presented. Free by cyclic groups are known to be coherent by work of Feighn and Handel. We show that many free by free groups (where the free groups have rank at least 2) are incoherent. Our techniques use fibrations of the group. ...
2019-05-07, godz. 16:15, 3180
Mahan Mj (Tata Institute of Fundamental Research)
Coarse Extrinsic Geometry and surface-by-free groups
JOINT WITH SIMONS SEMESTER The notion of distortion of finitely generated subgroups H of finitely generated groups G, introduced by Gromov, is a first step towards studying extrinsic geometry of subgroups in the coarse setup. When the group and subgroup are hyperbolic, finer information can be ...
2019-04-30, godz. 16:15, 3180
Marcin Sabok (McGill University, IMPAN)
JOINT WITH SIMONS SEMESTER In 1925, Tarski asked if a disc in the plane and a square of the same area are equidecomposable, i.e. if the disc can be partitioned into finitely many pieces which can be rearranged by isometries of the plane to form a square. In 1990, Laczkovich showed that Tarski&...
