Seminars in geometry/topology
The Geometry and Topology Seminar will be on Mondays 14:15 - 15:15 unless otherwise stated. Please also join us for some social time after the seminars! Get in touch with Abi if you would like to be added to the mailing list, give a talk yourself, or have someone in mind that you would like to invite.
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Spring 2023 - Upcoming Talks
This semester seminars will be on Mondays unless otherwise stated.
Topology Seminar Monday 06 February, 14:15-15:15, VA2 Varmeteknisk
Sira Gratz (Aarhus): Thick Subcategories and Lattices
Abstract: The computation of lattices of thick subcategories has emerged as a popular topic and serves as a more achievable analogue of classifying objects. Often one understands such lattices by describing them in terms of some associated topological space. However, in many representation theoretic examples this is not possible. I’ll explain what the obstruction is and introduce possible methods of addressing this issue. This talk is based on joint work with Greg Stevenson.
Topology Seminar Tuesday 14 February, 14:15-15:15
Lisbeth Fajstrup (Aalborg University): tbc
Monday 9 January postponed, 14:15-15:15
Alexander Berglund (Stockholm): tbc
Spring 2023 - Past Talks
Topology Seminar Monday 16 January, 14:15-15:15, VA2 Varmeteknisk
Kim Anders Frøyshov (Universitetet i Oslo): 4-manifolds and instanton homology
Abstract: The starting point for this talk is the by now classical diagonalization theorem of Donaldson, which says that if the intersection form of a closed oriented smooth 4-manifold X is definite, then the intersection form is diagonal over the integers. It is natural to ask which unimodular definite forms may occur as intersection form if X is allowed to have a fixed homology sphere Y as boundary. Attempts at adapting proofs of Donaldson's theorem to this situation (using either instantons, Seiberg-Witten monopoles, or Heegaard Floer theory) naturally lead to numerical invariants of Y defined in terms of various kinds of Floer homology of Y. These invariants constrain the "exoticness" of any definite form bounded by Y. I will review both classical and more recent results in this area and also discuss ongoing work of my own using mod 2 instanton homology.