Monday 30 August – Saturday 4 September 2010

To the memory of Graham Everest

The subject of this workshop has connections with
**logic**, **number theory** and **algebraic geometry**.

The main topic of **Definability in Number Theory**
is studying which sets and structures can be defined or interpreted
in the existential or first-order theory of rings and fields.
We are particularly interested in rings and fields which play a role in number theory.
Questions about definability have important applications for (un)decidability.
For example, the negative answer to Hilbert's Tenth Problem
followed from the fact that all recursively enumerable sets in **Z**
are existentially definable over **Z**.
Another example is the fact that **Z** is existentially definable inside **R**(*t*),
with the consequence that diophantine equations over **R**(*t*) are undecidable.

The following people have given a talk:

- Juliusz Brzezinski (Gothenburg and Chalmers)
- Paola D'Aquino (Napoli 2)
- Martin Davis (New York and Berkeley)
- Jeroen Demeyer (Ghent) — cancelled due to unforseen circumstances
- Kirsten Eisentraeger (Penn State)
- Arno Fehm (Jerusalem)
- James Freitag (Chicago)
- Harvey Friedman (Ohio State)
- Moshe Jarden (Tel Aviv)
- Jochen Koenigsmann (Oxford)
- Noa Lavi (Negev)
- Eva Leenknegt (Leuven)
- Hector Pasten (Concepción)
- Thanases Pheidas (Crete)
- Aharon Razon (Elta)
- Alexandra Shlapentokh (East Carolina)
- Alla Sirokofskich (Crete)
- Xavier Vidaux (Concepción)
- Olivier Wittenberg (ENS Paris)
- Alan Woods (Western Australia)

Titles, abstracts and slides can be found at the **schedule**.

View the **list of participants**.

- Jeroen Demeyer (Ghent)
- Jan Denef (Leuven)
- Jan Van Geel (Ghent)
- Xavier Vidaux (Concepción)
- Carlos Videla (Mount Royal, Calgary)

- Lien Boelaert (Ghent)
- Claudia Degroote (Ghent)
- Jeroen Demeyer (Ghent)
- Jan Van Geel (Ghent)

The meeting is funded by: