Northern German Algebraic Geometry Seminar
Bielefeld University
30-31 January 2025
Speakers
|
Gregorio Baldi (Jussieu) Anna Cadoret (Jussieu) Salvatore Floccari (Bielefeld) Jan Lange (Hanover) |
Angela Ortega (Berlin) Thomas Peternell (Bayreuth) Alessandra Sarti (Poitiers) |
Organisers
| Ana Botero | Eike Lau | Charles Vial |
NoGAGS
The Northern German Algebraic Geometry Seminar is a regular joint seminar of the algebraic geometry groups in Berlin, Bielefeld, Goettingen, Hamburg, Hanover, Leipzig and Oldenburg. Information on the previous meetings can be found here.Schedule
The first talk will be at 11am on Thursday and the last talk will finish at 3pm on Friday. The detailed schedule will be announced later.There will be a dinner on Thursday evening. (Unfortunately, we will not be able to cover the dinner costs for participants).
Registration
In order to organise badges, coffee breaks, and the conference dinner, we ask participants to register before 15 January 2025 by sending an email to Claudia Gaertner cgaertner@math.uni-bielefeld.de with their name and affiliation, and whether they intend to attend dinner.Abstracts
Gregorio Baldi
Title: The Noether-Lefschetz locus and the questions of Harris and Voisin
Abstract: After recalling the classical results on the distribution of the components of the NL locus from the 80s and early 90s, I will explain how they relate to the "completed Zilber-Pink philosophy" developed with B. Klingler and E. Ullmo. Armed with this viewpoint, we will show that the so called exceptional components are not Zarsiski dense in the moduli space of smooth surfaces of degree d. The novelty is that they, in some sense, they are explained by the presence of extra ‘’higher Hodge tensors’’. If time permits, I will sketch a new proof of this result (joint with D. Urbanik), which builds on Galois theory of foliations.
Anna Cadoret
Title: TBD
Abstract: TBD
Salvatore Floccari
Title: TBD
Abstract: TBD
Jan Lange
Title: On the rationality problem for hypersurfaces
Abstract: We prove that a very general hypersurface of degree $d \geq 4$ and dimension at most $(d+1)2^{d-4}$ does not admit a decomposition of the diagonal, in particular it is neither stably nor retract rational nor $\mathbb{A}^1$-connected. This joint work with Stefan Schreieder improves earlier results by Schreieder (2019) and Moe (2023).
Angela Ortega
Title: TBD
Abstract: TBD
Thomas Peternell
Title: Compactifications of homology cells and the complex projective space
Abstract: I will discuss the following problem: given a projective manifold X and a submanifold Y such X - Y is a homology cell, is X a projective space?
Alessandra Sarti
Title: Enriques varieties
Abstract: Enriques surfaces are special free quotients of K3 surfaces, i.e. these are the quotients of a K3 surface by a fixed point free involution. In higher dimension the notion can be generalized and one can introduce Enriques manifolds which share several properties with Enriques surfaces. In the first part of the talk I will discuss the existing definitions introduced by several authors and construct exemples as quotients of irreducible holomorphic symplectic manifolds and Calabi--Yau manifolds. In the second part I will discuss several recent results and I will then extend the notion of Enriques manifold to the singular setting, generalizing the notion of Log Enriques surface introduced by Oguiso and Zhang in the 90's. Most of the results I will present are contained in several joint works with S. Boissière, C. Camere and M. Nieper-Wisskirchen.
Location
All talks will take place in H10 in the main building of Bielefeld University.From the Bielefeld main train station, take the Stadtbahn 4 in direction of Lohmannshof and exit at the stop "Universität"; you will have to exit the train station building and cross the street to get to the Stadtbahn station.
We ask that participant take care of their accommodation. There are a number of hotels in the city center with easy access to the Stadtbahn. For example, the Altstadt Hotel, Comfort Garni and ibis Styles are each located about a 3 minute walk from the Stadtbahn station "Jahnplatz", another stop of the Stadtbahn 4. Should you require assistance with booking an accommodation, please contact Claudia Gärtner (first-come-first-serve).