## 2008

### Intercity Number Theory Seminar

15 February, Leiden. Room 407- 12:15–13:00
- Hendrik Lenstra, Degrees of field automorphisms
In December 2020, Peter Scholze posed a challenge to formally verify the main theorem on liquid ℝ-vector spaces, which is part of his joint work with Dustin Clausen on condensed mathematics. I took up this challenge with a team of mathematicians to verify the theorem in the Lean proof assistant. Half a year later, we reached a major milestone, and our expectation is that shortly we will have completed the full challenge. In this talk I will give a brief motivation for condensed/liquid mathematics, a demonstration of the Lean proof assistant, and discuss our experiences formalizing state-of-the-art research in mathematics.
- 14:00–14:45
- Jonathan Hanke, The 290-Theorem and Representing Numbers by Quadratic Forms
In December 2020, Peter Scholze posed a challenge to formally verify the main theorem on liquid ℝ-vector spaces, which is part of his joint work with Dustin Clausen on condensed mathematics. I took up this challenge with a team of mathematicians to verify the theorem in the Lean proof assistant. Half a year later, we reached a major milestone, and our expectation is that shortly we will have completed the full challenge. In this talk I will give a brief motivation for condensed/liquid mathematics, a demonstration of the Lean proof assistant, and discuss our experiences formalizing state-of-the-art research in mathematics.
- 15:00–15:45
- Chia-Fu Yu, On geometric mass formulas
In December 2020, Peter Scholze posed a challenge to formally verify the main theorem on liquid ℝ-vector spaces, which is part of his joint work with Dustin Clausen on condensed mathematics. I took up this challenge with a team of mathematicians to verify the theorem in the Lean proof assistant. Half a year later, we reached a major milestone, and our expectation is that shortly we will have completed the full challenge. In this talk I will give a brief motivation for condensed/liquid mathematics, a demonstration of the Lean proof assistant, and discuss our experiences formalizing state-of-the-art research in mathematics.
- 16:00–16:45
- Lenny Taelman, Cubic rings, cubic forms

### L-functions and friends

29 February, VU Amsterdam. Room M129. Today's program is part of Rob de Jeu's Algebra seminar. The seminar finishes early because of the inaugural lecture of Rob van der Vorst at 15:45.- 11:00–12:00
- Tejaswi Navilarekallu, Galois actions and L-values
- 13:00–14:00
- Don Zagier, Modular Green's functions
- 14:15–15:15
- Xavier-François Roblot, Computing values of
*p*-adic*L*-functions over a real quadratic field

### Intercity Number Theory Seminar: Van der Kallen Celebration

14 March, Utrecht. room BBL 160. Today's seminar is dedicated to the 61st birthday of Wilberd van der Kallen. After the talks at 4PM there will be a reception in the library.- 10:30–11:30
- Jan Draisma, Phylogenetic tree models and classical invariant theory
- 11:45–12:45
- Wim Hesselink, Euclidean skeletons of digital images in linear time by the integer medial axis transform
- 13:45–14:45
- Johnny Edwards, The chocolate bar conjecture
- 15:00–16:00
- Vincent Franjou, Finite generation for (higher) invariants

### Intercity Number Theory Seminar

4 April, Groningen. room 105 of the new Bernoulliborg building, Nijenborgh 9: the big blue building on your right when bus 15 enters the campus.- 11:45–12:45
- Cécile Poirier, Stacks, vector bundles and `geometric Langlands'.
- 13:30–14:30
- Fai-Lung Tsang, Skew rings and geometric method in convolutional codes
- 14:45–15:45
- Steve Meagher, Freiburg), Genus three curves revisited
- 16:00–17:00
- Evgeny Verbitskiy, Marius van der Put, Abelian sandpiles and discrete difference equations

### Intercity Number Theory Seminar: genus 2 day

18 April, Utrecht. room BBL 160 (Buys-Ballot-Lab)- 11:00–11:50
- Marco Streng, Igusa class polynomials
- 12:00–12:50
- Jeroen Sijsling, Humbert Surfaces and Shimura Curves
- 14:30–15:20
- Andrew Hone, Somos Sequences and genus two addition formulae
- 15:30–16:20
- Dan Bernstein, Hyperelliptic-curve cryptography

### Intercity Number Theory Seminar

9 May, Leiden. room 207 Huygens building- 12:00–13:00
- Hugo Chapdelaine, An introduction to the 12th Hilbert problem
- 14:00–16:00
- Cristian Popescu, On the Coates-Sinnott Conjectures
- 16:15–17:15
- Remke Kloosterman, Computing the Mordell-Weil group of elliptic threefolds

### Intercity number theory seminar

12 September, Leiden. Room 412- 14:00–14:45
- Gabriel Chênevert, The quartic fields method
- 15:00–15:45
- Sylvain Brochard, Picard functor and algebraic stack
- 16:00–16:45
- Ronald van Luijk, Density of rational points on diagonal quartic surfaces

### Standard models of finite fields

26 September, Nijmegen.- 11:30–12:15
- Frank Lübeck, Conway polynomials
- 13:30–14:15
- Wieb Bosma, Dealing with finite fields in Magma
- 14:45–15:30
- Bart de Smit, Consistent isomorphisms between finite fields
- 16:00–16:45
- Hendrik Lenstra, Defining
**F**_{q}

*Intercity number theory seminar*

*10 October, Leiden. The first talk is in room 402 and the others in room 174.*

- 12:00–12:45
- Karen Aardal, Integer programming and some connections to number theory
- 13:45–14:30
- Andrea Montanari, Torus based cryptography
- 14:45–15:30
- Willemien Ekkelkamp, Predicting the sieving effort for the number field sieve

*Intercity number theory seminar*

*14 November, Groningen. room 267 of the mathematics building Bernoulliborg*

- 11:30–12:30
- Andrey Timofeev, Index-calculus in the Brauer groups with arithmetic applications
- 13:30–14:30
- Felix Fontein, A Concise Interpretation of the Infrastructure of a Global Field
- 14:45–15:45
- Marius van der Put, A geometric approach to Painlevé differential equations
- 16:00–17:00
- Jaap Top, Maximal curves over finite fields

*Intercity number theory seminar*

*12 December, UvA Amsterdam. Morning program in room P0.19 of the Euclides building.*

Tom Koornwinder gives his farewell address in the afternoon at 15:00.

Tom Koornwinder gives his farewell address in the afternoon at 15:00.

- 10:30–11:15
- Arjen Stolk, Fast group operations on Jacobians
- 11:30–12:15
- Peter Bruin, Finding random points on curves over finite fields
- 12:30–13:15
- Sylvain Brochard, On De Smit's conjecture on flatness on Artin rings