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Barcelona Algebraic Topology Group

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Friday's Topology Seminar 2018-19

Speaker: Marc Stephan (MPI, Bonn)
Title: A multiplicative spectral sequence for free p-group actions
Room Seminar C3b
Date: Friday May 24th, 12h-13h

Abstract: Carlsson conjectured that if a finite CW complex admits a free action by an elementary abelian p-group G of rank n, then the sum of its mod-p Betti numbers is at least 2^n. In 2017, Iyengar and Walker constructed equivariant chain complexes that are counterexamples to an algebraic version of Carlsson’s conjecture. This raised the question if these chain complexes can be realized topologically by free G-spaces to produce counterexamples to Carlsson’s conjecture. In this talk, I will explain multiplicative properties of the spectral sequence obtained by filtering the mod-p cochains of a space with a free p-group action by powers of the augmentation ideal and deduce that the counterexamples can not be realized topologically. This is joint work with Henrik Rüping.

See the calendar for upcoming events.

Friday's Topology Seminar 2017-2018

Speaker: Nitu Kitchloo (Johns Hopkins University)
Title: Stability for Kac-Moody Groups
Place: C3b/158
20th July at 12:00

Abstract: In the class of Kac-Moody groups, one can extend all the exceptional families of compact Lie groups yielding infinite families, as well as other infinite families. We will show that these exceptional families stabilize in a homotopical sense and that the (co)homology of their classifying spaces is torsion free for all but a finite set of primes that is determined by the family (and not the individual groups in the family).

See the calendar for upcoming events.

Friday's Topology Seminar 2016-2017

Speaker: Ramón Flores (Universidad de Sevilla)
Title: Espacios clasificadores de grupos de trenzas.
Place: Seminari C1/366
28th July at 10:00.
En esta charla mostraremos cómo se puede calcular la dimensión del espacio clasificador de los grupos de trenzas respecto de la familia de grupos virtualmente cíclicos. Las herramientas utilizadas incluyen el modelo de Lück-Weiermann de estos espacios, la clasificación de trenzas de Nielsen-Thurston, y resultados homológicos sobre los conmensuradores de los subgrupos cíclicos.

See the calendar for upcoming events.

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