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Tuesday, November 11, 2025

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4:00pm
Pseudo-Anosov subgroups of surface bundles over tori [3]
11/11/2025 - 4:30pm

In 2002, Farb and Mosher introduced the notion of convex cocompactness in the mapping class group to capture coarse geometric information of the associated surface group extensions. Convex cocompact subgroups are necessarily finitely generated and purely pseudo-Anosov, but it is an open question whether the converse is true. Several partial results are known in certain settings, however. For example, work of Dowdall, Kent, Leininger, Russell, and Schleimer give a positive answer for subgroups of fibered 3-manifold groups (aka surface-by-cyclic extensions) naturally embedded in punctured mapping class groups via the Birman exact sequence. We present a generalization of this in the setting of surface-by-abelian extensions.

Location:
KT 207
 
Secant sheaves and Weil classes I [4]
11/11/2025 - 4:30pm

We will describe a general strategy for proving the algebraicity of the Hodge Weil classes on abelian varieties of Weil type. The latter are even dimensional abelian varieties admitting a suitable embedding of a CM number field in their rational endomorphism ring. We will describe the implementation of the strategy for abelian varieties of dimension 4 and 6, and why it implies the Hodge conjecture for abelian varieties of dimension at most 5.

Location:
KT 801
 
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[1] https://calendar.math.yale.edu/calendar/grid/day/2025-11-10 [2] https://calendar.math.yale.edu/calendar/grid/day/2025-11-12 [3] https://calendar.math.yale.edu/event/pseudo-anosov-subgroups-surface-bundles-over-tori [4] https://calendar.math.yale.edu/event/secant-sheaves-and-weil-classes-i [5] https://calendar.math.yale.edu/print/list/calendar/grid/day [6] webcal://calendar.math.yale.edu/calendar/export.ics