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Geometry-Topology Seminar

Thursday, November 12, 2020 - 4:30pm

Bena Tshishiku

Brown

Location

University of Pennsylvania

Zoom

The Zoom link is: https://upenn.zoom.us/j/91890239234 This same Zoom link will apply for future talks as well. It is set to open at 4 PM so that speakers can come on early and check out their technology setups. The talks will begin at 4:30 PM. We will also stay afterwards, say from 5:30 - 6 PM to chat with one another, as an online substitute for going out to dinner with our speakers. We encourage everyone to have a nice bottle of wine at hand for that social half hour. For further information about the seminar, please contact Mona Merling (mmerling@math.upenn.edu), Davi Maximo (dmaxim@math.upenn.edu) or Herman Gluck (gluck@math.upenn.edu).

We give a construction of nontrivial cohomology classes of arithmetic subgroups of SO(p,q). These classes lie just outside the stable range and are dual to geometric cycles in the locally symmetric space. The classes we construct have a nice interpretation as characteristic classes, and as an application we obtain nontrivial characteristic classes for certain manifold bundles that are not in the algebra generated by the stable classes.