Squares in Dortmund
31 March - 4 April 2025
A conference on quadratic forms and related topics -
on the occasion of Detlev Hoffmann's 64th birthday
Invited Speakers
- Olivier Benoist (Paris)
- Greg Blekherman (Georgia Tech)
- David Leep (Kentucky)
- Vlerë Mehmeti (Paris)
- Anne Quéguiner-Mathieu (Paris)
- Gabriele Nebe (Aachen)
- R. Parimala (Emory)
- Federico Scavia (Paris)
- Stephen Scully (Victoria)
- Alexander Vishik (Nottingham)
Organizers
Karim Johannes BecherDaniel Plaumann
The conference is supported by Deutsche Forschungsgemeinschaft.
Registration and Conference Fee
Please register by email to and indicate the following:Name:
Affiliation:
Status: student/postdoc/professor/etc.; this information is important for our funding.
Talk: If you wish to give a 30 minute contributed talk, please send us a tentative title and abstract. We have a limited number of slots and will get in touch with participants interested in giving a talk.
Financial support: We have limited funds to contribute to travel and accommodation for young participants without (sufficient) funding. Please indicate if you request financial support. Final decisions and reimbursements can only be made after the conference.
All participants (except invited speakers) are requested to pay a conference fee of 150 Euros. (The exact amount may still change slightly.) Registered participants will later receive an email with payment instructions.
This money will be used for expenses that cannot be covered by other funding, in particular coffee breaks, lunch, excursion and conference dinner.
The deadline for registration is February 15.
Venue
All lectures will take place at TU Dortmund in room M/E29 on the ground floor of the Mathetower ("Mathematik Hauptgebäude/Audimax").If you arrive by S-Bahn, please exit the S-Bahn station up the escalators, then up the stairs and past the construction site. (Just follow the crowds). The Mathetower is the tall building with the "TU" sign on top.
Accommodation
It is easy to get to campus by metro (S-Bahn) from the central station (Dortmund Hbf), so staying in the city center is a good option.NH Hotel Dortmund is comfortable and close to the station. (The invited speakers will be staying here.)
We have a limited number of pre-reserved rooms, which can be booked using the following link:
https://www.nh-hotels.com/de/event/tu-dortmund-university
A&O Hostels Dortmund Hauptbahnhof, a less expensive hostel/hotel, which also offers shared rooms at lower rates.
Courtyard (Marriott) Dortmund, the only hotel right on campus, about ten minutes walk from the conference venue.
Airbnb rentals are also available in Dortmund.
Participants are asked to make their own arrangements, but we will be happy to answer questions or provide assistance if needed ().
Please note that Dortmund regularly hosts large trade fairs, as well as football games. So while plenty of rooms are available at the moment, it is advisable to make a reservation in time.
Getting to Dortmund
by train: to Dortmund Hbfby plane: Dortmund Airport is served directly from a small number of European destinations.
From Düsseldorf Airport, trains are frequent and take about 45 minutes.
From Frankfurt Airport, ICE trains take about 140 minutes (direct or with one change),with at least one connection per hour.
Getting to Campus
From Dortmund Central Station: Take S-Bahn Line 1 (Direction Solingen/Bochum/Essen, but there is only one direction) to "Dortmund Universität" from Track 7.You need to buy a ticket from a VRR ticket machine (or press the VRR button on a DB ticket machine), price level A3.
Ticket machines are in the main station hall.
Tickets can also be bought with the DB App.
Trains take 7 minutes and run every 15 minutes. There are frequent delays, unfortunately, so please plan accordingly, if possible. (If you have experience using the Deutsche Bahn App, it may make sense to check the DB App for delays before you leave.)
For information on parking on campus etc, see also
Kontakt und Anreise (TU Dortmund)
Talks and Schedule
O. Benoist: Sums of squares of analytic functionsG. Blekherman: Sums of squares and stubborn polynomials on curves (provisional)
D. Leep: Systems of quadratic forms and u-invariants
V. Mehmeti: Local-global principles and the u-invariant (provisional)
A. Quéguiner-Mathieu: Higher Tate trace and classification of Chow motives
G. Nebe: Orthogonal representations of finite groups
R. Parimala: Projective homogeneous spaces and Hasse principle (provisional)
F. Scavia: The lifting problem for Galois representations
S. Scully: On the holes in I^n for symmetric bilinear forms (provisional)
A. Vishik: Varieties and pure symbols (provisional)
Monday, 31 March
| 9:00 | Welcome | |
| 9:15-10:15 | Invited Talk | |
| - Coffee break - | ||
| 10:45-11:15 | Contributed Talk | |
| 11:30-12:30 | Invited Talk | |
| - Lunch - | ||
| 14:30-15:00 | Contributed Talk | |
| 15:15-15:45 | Contributed Talk | |
| - Coffee break - | ||
| 16:15-16:45 | Contributed Talk |
Tuesday, 1 April
| 9:15-10:15 | Invited Talk | |
| - Coffee break - | ||
| 10:45-11:15 | Contributed Talk | |
| 11:30-12:30 | Invited Talk | |
| - Lunch - | ||
| 14:30-15:00 | Contributed Talk | |
| 15:15-15:45 | Contributed Talk | |
| - Coffee break - | ||
| 16:15-16:45 | Contributed Talk |
Wednesday, 2 April
| 9:00 | Welcome | |
| 9:15-10:15 | Invited Talk | |
| - Coffee break - | ||
| 10:45-11:15 | Contributed Talk | |
| 11:30-12:30 | Invited Talk | |
| - Lunch - | ||
| - Afternoon excursion - | ||
| - Conference Dinner - |
Thursday, 3 April
| 9:15-10:15 | Invited Talk | |
| - Coffee break - | ||
| 10:45-11:15 | Contributed Talk | |
| 11:30-12:30 | Invited Talk | |
| - Lunch - | ||
| 14:30-15:00 | Contributed Talk | |
| 15:15-15:45 | Contributed Talk | |
| - Coffee break - | ||
| 16:15-16:45 | Contributed Talk |
Friday, 4 April
| 9:00 | Welcome | |
| 9:15-10:15 | Invited Talk | |
| - Coffee break - | ||
| 10:45-11:15 | Contributed Talk | |
| 11:30-12:30 | Invited Talk | |
| 12:45-13:15 | Contributed Talk | |
| - Lunch - |
