Seminar: Symplektische Geometrie / Symplectic Geometry — Sommersemester 2025, HU Berlin

What?

This is a working group seminar run by Chris Wendl, Klaus Mohnke, and Thomas Walpuski on recent developments in symplectic geometry and related areas. Participants are expected to be familiar with the basics of symplectic geometry, including some knowledge of holomorphic curves and/or Floer-type theories. The seminar is conducted in English.

When and where?

For the 2025 summer semester, the seminar meets on Mondays, 13:15-14:45 in room 2.006 at the HU math department (Rudower Chaussee 25). See below for a precise schedule.

New feature this semester: There will be coffee and cookies after the seminar!

If you plan to participate in the seminar, please join the moodle (the enrollment key is "cookies"). The moodle will be used for occasional time-sensitive announcements. Users affiliated with the HU can access moodle using their HU username and password. Non-HU users can access it by following this link and then clicking on "Create new account".


The seminar will begin in the fourth week of the semester.

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Monday April 14, 2025 No seminar
Monday April 21, 2025 No seminar due to the Easter holiday
Monday April 28, 2025 No seminar due to the knot theory workshop in Potsdam
Monday May 5, 2025
13:15-14:45
RUD 25, Room 2.006
Speaker: Gerard Bargallo
Topic: Fuk, fragile symmetries
Abstract: In his thesis, Seidel studied symmetries of symplectic manifolds that are "fragile" (with respect to the symplectic form) to explain instances of non-trivial symplectic phenomena that are however smoothly invisible. For example, this ultimately explains why Lagrangian spheres can be smoothly unknotted but symplectically knotted. My aim in this talk is to explain why Floer theory (which I will introduce) is the right tool to deal with these kinds of problems. We will extrapolate basic features of Floer (co)homology in this context to features of the Fukaya category, which is one of the central invariants of symplectic manifolds and one of the two key parts of homological mirror symmetry, for example. If time permits (i.e. if I managed to understand all the above well enough to give succinct explanations) I may quickly explain how to compute Floer homology of cleanly intersecting Lagrangians (cute and geometric spectral sequence argument).
Friday May 9, 2025
13:30-15:00
RUD 25, Room 1.023
(BMS Seminar Room)
Speaker: Agustin Moreno (Heidelberg)
Topic: Exotic contact structures on the sphere and beyond
Abstract: By work of Eliashberg in dimension 3 and Borman-Eliashberg-Murphy in higher dimensions, there are two flavors of contact structures: tight (geometric/rigid), and overtwisted (topological/flexible). Tight contact structures are much harder to classify than the overtwisted ones (which satisfy an h-principle, and so are abundant). One way to understand tight structures is via their symplectic fillings. In this talk, I will explain how in dimension at least 5, the odd-dimensional sphere admits contact structures which are exotic from a symplectic point of view, namely they are tight but admit no (strong) symplectic filling. This is in stark contrast to the three-dimensional case, as Eliashberg showed there is a unique tight contact structure on the 3-sphere (which is fillable). Time permitting, I will discuss applications to arbitrary topology, and to different flavors of fillability. This is based on joint work with Jonathan Bowden, Fabio Gironella and Zhengyi Zhou.
Monday May 12, 2025 No seminar due to special talk on Friday 9.05 instead
Monday May 19, 2025
13:15-14:45
RUD 25, Room 2.006
Speaker: Julio Sampietro Christ (Paris-Saclay)
Topic: Equivariant Lagrangian Floer homology and the Cartan isomorphism
Abstract: In this talk we’ll go from classical equivariant homology to equivariant Lagrangian Floer homology, making stops at various places such as the land of quilts. Then we will prove the Floer version of the Cartan isomorphism and, if time permits, give some applications.
Monday May 26, 2025
13:15-14:45
RUD 25, Room 2.006
Speaker: Jacek Rzemieniecki
Topic: Locality in the Fukaya category of a hyperkähler manifold
Monday June 2, 2025
13:15-14:45
RUD 25, Room 2.006
Speaker: David Suchodoll
Topic: Multiplicity of knot floer order
Monday June 9, 2025 No seminar due to the Pentecost holiday
Wednesday June 11, 2025
16:30-18:00
RUD 25, Room 1.013
Speaker: Kenny Blakey (MIT)
Topic: TBA
Monday June 16, 2025
13:15-14:45
RUD 25, Room 2.006
Speaker: TBA
Topic: TBA
Monday June 23, 2025
13:15-14:45
RUD 25, Room 2.006
Speaker: TBA
Topic: TBA
Monday June 30, 2025
13:15-14:45
RUD 25, Room 2.006
Speaker: Amanda Hirschi (Sorbonne)
Topic: TBA
Wednesday July 2, 2025
16:30-18:00
RUD 25, Room 1.013
Speaker: Amanda Hirschi (Sorbonne)
Topic: TBA
Friday July 4, 2025 Berlin-Hamburg Symplectic Geometry Seminar meeting in Berlin, see https://www.math.uni-hamburg.de/home/latschev/BH-symp.html
Monday July 7, 2025
13:15-14:45
RUD 25, Room 2.006
Speaker: Johannes Hauber
Topic: TBA
Monday July 14, 2025
13:15-14:45
RUD 25, Room 2.006
Speaker: TBA
Topic: TBA

last semester's symplectic seminar