Positivity, Valuations, and Quadratic Forms

Universität Konstanz

1 - 6 October 2009

[ Invited Speakers | Schedule | Talks | Participants | Getting to Konstanz | Accommodation | Getting around | Sights | Restaurants | Bars | Contacts ]

The aim of this conference is bringing together mathematicians from three disciplines within algebra, namely Real Algebra, Valuation Theory, and Quadratic Form Theory. These three fields have been in permanent interaction, but conferences specifically devoted to those interactions have been quite rare in recent years.

The conference is organised by Karim Johannes Becher, Tim Netzer, Daniel Plaumann, and Claus Scheiderer.
It is supported by the Deutsche Forschungsgemeinschaft and by the Zukunftskolleg at the University of Konstanz.

The deadline for registration has passed. If you are interested in participating and have not yet registered, please contact the organisers as soon as possible ( ).

Please note that there will be a conference fee of 100 Euros. Lunch at the University and the conference dinner are included.

Invited Speakers

Ricardo Baeza (Universidad de Talca, Chile)
Wulf-Dieter Geyer (Universität Erlangen-Nürnberg, Germany)
Julia Hartmann (RWTH Aachen, Germany)
Detlev Hoffmann (University of Nottingham, UK)
Igor Klep (Univerza v Ljubljana, Slovenia)
Jochen Koenigsmann (University of Oxford, UK)
Monique Laurent (CWI Amsterdam, Netherlands)
Peter J. Roquette (Universität Heidelberg, Germany)
Konrad Schmüdgen (Universität Leipzig, Germany)
Jean-Pierre Tignol (Université catholique de Louvain, Belgium)
Lou van den Dries (University of Illinois at Urbana-Champaign, USA)


Image: Universität Konstanz - Photographer: Michael Latz

Lectures will start on Thursday morning and end on Tuesday afternoon.

Conference schedule and abstracts (pdf)

Following the afternoon session on Friday, 2 October, there will be a reception in honour of Alexander Prestel.

The conference dinner will take place on Saturday, 3 October, 19:30 at the Konzil restaurant.

On Sunday, 4 October there will be no scientific programme. A joint excursion to the Island of Reichenau is planned for that day. We will travel to the island by boat (approx. one hour each way) and stay there for the afternoon, with enough time for a walk around the island, a visit to the monasteries, and lunch.


F. Acquistapace Positive semidefinite analytic functions
R. Baeza Generalized Hermite Constants
H. Bosse Non-Negative Polynomials that are not Sums of Squares
J. Cimpric A method for computing lowest eigenvalues of symmetric polynomial differential operators by semidefinite programming
J. Demeyer Hilbert's Tenth Problem for function fields over valued fields
M. Dickmann Faithfully quadratic rings
R. Flatley Trace forms of symbol algebras
W.-D. Geyer Patching
P. Gładki Certain quotient spaces of spaces of orderings and their inverse limits
J. Hartmann Local Global Principles for Quadratic Forms
D. Hoffmann Something old and something new about u
M. Karoubi Periodicity in hermitian K-theory
I. Klep Free real algebraic geometry
M. Knebusch Semirings with bounds
J. KoenigsmannFields with the Galois group of Q
M. Laurent Optimization over polynomials with sums of squares and moment matrices
N. Lavi Ganzstellensatz for open sets in real closed fields
H. Nguyen Polynomials non-negative on non-compact subsets of the plane
A. Pfister An elementary and constructive proof of Hilbert's theorm on ternary quartics
J. Povh Ncsostools: a computer algebra system for symbolic and numerical computation with nc polynomials
R. Quarez Effective tridiagonal determinantal representation for univariate polynomials and real roots counting
P. Roquette Arf invariants of quadratic forms in historical perspective
J. Savchuk Positivstellensätze for some algebras of matrices
K. Schmüdgen Positivity, Sums of Squares and Positivstellensätze for *-Algebras
A. SmithFast Positivity Testing using Bernstein Expansion
T. Theobald Valuations and tropical bases
M. Thomas Parameterization and the rational points of definable sets
J.-P. Tignol Valuations on central simple algebras
T. Unger Torsion in Witt groups and sums of hermitian squares
S. Wagner A decision problem for real multivariate polynomials
L. van den Dries Immediate extensions of H-fields

Registered participants

Acquistapace, Francesca (Pisa)
Astier, Vincent (Dublin)
Augustin, Doris (Regensburg)
Averkov, Gennadiy (Magdeburg)
Baeza, Ricardo (Talca)
Barth, Dominic (Konstanz)
Barthel, Gottfried (Konstanz)
Becker, Eberhard (Dortmund)
Beke, Sofie (Ghent)
Boelaert, Lien (Ghent)
Bosse, Hartwig (Frankfurt)
Bröcker, Ludwig (Münster)
Broglia, Fabrizio (Pisa)
Burgdorf, Sabine (Konstanz)
Cafuta, Kristijan (Ljubljana)
Callens, Elizabeth (Ghent)
Capco, Jose (Passau/Wien)
Cimpric, Jaka (Ljubljana)
Conversano, Annalisa (Konstanz)
Degroote, Claudia (Ghent)
Demeyer, Jeroen (Ghent)
Dickmann, Max (Paris)
Dolphin, Andrew (Konstanz)
Dupont, Katharina (Konstanz)
Flatley, Ronan (Dublin)
Friedrichsdorf, Ulf (Konstanz)
Garloff, Jürgen (Konstanz)
Geyer, Wulf-Dieter (Erlangen)
Gładki, Paweł (Santa Barbara)
Gondard, Danielle (Paris)
Grimm, David (Konstanz)
Hanselka, Christoph (Konstanz)
Hartmann, Julia (Aachen)
Hoffmann, Detlev (Nottingham)
Huber, Roland (Wuppertal)
Izhakian, Zur (Tel Aviv)
Jensen, Christian (Copenhagen)
Kaiser, Tobias (Passau)
Karoubi, Max (Paris)
Klep, Igor (Ljubljana)
Knebusch, Manfred (Regensburg)
Knus, Max-Albert (Zürich)
Koenigsmann, Jochen (Oxford)
Kuhlmann, Salma (Konstanz)
Kurdyka, Krzysztof (Chambéry)
Laurent, Monique (Amsterdam)
Lavi, Noa (Be'er Sheva)
Marshall, Murray (Saskatoon)
Matusinski, Mickael (Konstanz)
Michalska, Maria (Chambéry)
Nguyen, Ha (Atlanta)
O'Shea, James (Dublin/Konstanz)
Pernazza, Ludovico (Pavia)
Pfister, Albrecht (Mainz)
Povh, Janez (Ljubljana)
Powers, Vicki (Atlanta)
Prestel, Alexander (Konstanz)
Prinzen, Lukas (Konstanz)
Quarez, Ronan (Rennes)
Raczek, Melanie (Louvain-la-Neuve)
Riener, Cordian (Frankfurt)
Roquette, Peter (Heidelberg)
Savchuk, Yuriy (Leipzig)
Scharlau, Rudolf (Dortmund)
Schmüdgen, Konrad (Leipzig)
Schwartz, Niels (Passau)
Schweighofer, Markus (Konstanz)
Sinn, Rainer (Konstanz)
Smith, Andrew (Konstanz)
Stöckler, Joachim (Dortmund)
Szafraniec, Franciszek (Kraków)
Theobald, Thorsten (Frankfurt)
Thomas, Margaret (Oxford/Konstanz)
Tignol, Jean-Pierre (Louvain-la-Neuve)
Unger, Thomas (Dublin)
Vinnikov, Victor (Be'er Sheva)
Wagner, Sven (Konstanz)
Wenzel, Sebastian (Konstanz)
van den Dries, Lou (Urbana)

Getting to Konstanz

By train: The webpage of the Deutsche Bahn has an online timetable that also works for connections from abroad.

From Zürich Airport: Train service to Konstanz is excellent, including one direct train per hour. Please check the above website of the Deutsche Bahn.
From Friedrichshafen Airport: There are several more or less equivalent possibilities: 1) by train via Radolfzell 2) by Catamaran 3) by ferry via Meersburg.

By car: Please note that free parking can be hard to find in Konstanz. If you have not been in touch with us about this, you should check whether your hotel provides parking space. Parking at the university is availabe for 1.50 euros per day.


If you are staying in one of the conference hotels, you should have received an email from the organizers informing you of the details. If you wish to change your reservation, you should contact the hotel directly. If you need assistance, do not hestiate to contact us.

Likewise, if you are a young researcher staying in one of the holiday apartments, you should have received email from us.

For your convenience, here are links to the hotel webpages:

Hotel Hirschen
Hotel Petershof
Hotel Schiff am See

All of the hotels are close to bus stops with direct service to the university. The town center, too, is easy to reach by bus, or is within walking distance (from Hirschen and Petershof). The town of Konstanz charges a fee of 1.50 Euros per night from all guests in addition to the hotel costs. In return, the use of busses is free.

Getting around

The following document contains instructions for getting to and around the university, as well as some general information:

Getting around and practical information for participants (pdf)

All talks will take place in lecture room A 704.

Bus timetables
Interactive bus map - Useful for finding the way to your respective bus stops


For general information, you can consult the site of the tourist information Konstanz .

Sights worth a visit in the evening after the lectures are for example:

Garden Island of Mainau, just a short walk (about 20 minutes) away from the university. Much more pleasant in the evening than in the daytime. If you book a table at the Restaurant "Schwedenschenke", you do not have to pay the entrance fee.

Cathedral of Konstanz; be sure to visit the cloister; the view from the tower is great.


Defne, Theodor-Heuss-Strasse 20, just a short walk from the bus stop "Zähringerplatz"; turkish food, very reasonable prices

Tolle Knolle, right next to Hotel Hirschen , Bodanplatz 9; everything you can do with potatoes (but not only), medium prices

Old Mary's Pub, Kreuzlinger Str. 19, Irish pub with an Italian cook, Pizza but also some good local food ("Duennele")

Some other recommendations:

Traube, Fischerstr. 4, Konstanz/Staad, traditional German pub.

Gasthaus Wallgut, Schottenstr. 44, Very good traditional German food, moderate prices.

Don Alfredo, Fischerstr. 4, Konstanz/Staad, Italian cuisine. (closed until Sunday, 4 October)

Schiff am See , William Graf Platz 2, Konstanz/Staad.

Restaurant Pinocchio, Italian cuisine, good but not cheap.


Some bars located in the historic centre:

Klimperkasten, Bodanstrasse 40.

Seekuh, Konzilstr. 1.

Brauhaus Johannes Albrecht, Konradigasse 2. Home made beer.

"Manuskript", Rheingasse 4, excellent wines and chocolates, low prices; located in the "Niederburg", the oldest part of town.

From the harbour, you will have a good view over the Lake of Konstanz. Several restaurants and bars are situated here.


Andrea Barjasic (Secretary)
Phone: +49 7531 88 2572

last change: 5 October 2009