## 2009

### Intercity number theory seminar and the inaugural lecture of Gunther Cornelissen

16 January, Utrecht. See announcement for details- 10:00–10:50
- Yiannis Petridis, Primes, prime geodesics and lattice points
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.
- 10:55–11:45
- Wladimir Pribitkin, The signs they are a-changin'
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.
- 13:30–14:20
- Gautam Chinta, Zeta functions, heat kernels and spectral asymptotics on degenerating families of discrete tori
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.
- 14:25–15:15
- Don Zagier, New constructions of mock modular forms
- 16:15–17:00
- Gunther Cornelissen, Het meten van dubbelzinnigheid

### Intercity number theory seminar

13 February, Leiden. Today's program is dedicated to the visit of five number theorists from Taiwan to Leiden. See also this week's colloquium lecture. The first lecture is in room 403, the others in room 402.- 11:30–12:20
- Yifan Yang, Construction and application of a class of modular functions
- 13:30–14:20
- Chieh-Yu Chang, On periods and logarithms for Drinfeld modules of rank 2
- 14:30–15:20
- Shu-Yen Pan, On local theta correspondence of supercuspidal representations
- 15:30–16:20
- Jeng-Daw Yu, Ordinary crystals with logarithmic poles

### Intercity number theory seminar

6 March, Delft. Snijderzaal- 11:00–12:00
- Tom Schmidt, Mediants of Rosen fractions and Hurwitz constants of Hecke groups
- 13:30–14:30
- Michel Dekking, Algebraic differences of random Cantor sets
- 15:00–16:00
- Dieter Mayer, The transfer operator approach to Selberg`s zeta function for Hecke triangle groups
*G*_{q} - 16:00–17:00
- Charlene Kalle, Expansions and Tilings

### Joint DIAMANT / GQT seminar

20 March, Utrecht.Program of four lectures by Spencer Bloch, Rob de Jeu, Alex Quintero Velez, Dmitri Orlov.

### Hendrik Lenstra's sixtieth birthday

24 April, Leiden.A special day at the occasion of Hendrik Lenstra's sixtieth birthday will be held on April 24 in Leiden. The morning program contains two mathematical talks and is part of the workshop Counting Points on Varieties. The afternoon will feature more personal talks by friends and colleagues of Hendrik Lenstra. Everybody is welcome to attend.

Morning program in the De Sitterzaal, Oort building:

- 9:15: coffee
- 9:45: opening
- 9:50 - 10:40: Carl Pomerance (Dartmouth)
- 10:50 -11:40: Manjul Bhargava (Princeton)

Afternoon program in the Lorentzzaal (A144) Kamerlingh Onnes Gebouw, Steenschuur 25, Leiden.

- 14:00 - 14:25: Ed Schaefer (Santa Clara)
- 14:30 - 14:55: Everett Howe (San Diego)
- 15:00: coffee
- 15:30 - 15:55: Johannes Buchmann (Darmstadt)
- 16:00 - 16:25: Richard Groenewegen (London)
- 16:30: closing and drinks

Organisers: Ronald van Luijk, Bart de Smit, Peter Stevenhagen, Lenny Taelman.

- 09:50–10:40
- Carl Pomerance, Sociable numbers
- 10:50–11:40
- Manjul Bhargava, Galois closure for rings
- 14:00–14:25
- Ed Schaefer, I started feeling sorry for the problem.
- 14:30–14:55
- Everett Howe, Channeling your advisor
- 15:30–15:55
- Johannes Buchmann, Hendrik Lenstra and cryptography
- 16:00–16:25
- Richard Groenewegen, A sense of reality

### Intercity number theory seminar

8 May, Groningen. Room 267, Bernoulliborg- 11:45–12:30
- Steve Meagher, Freiburg), Equations for Abelian varieties with a prescribed number of points over a finite field.
- 13:15–14:00
- Vivija Ceprkalo, Elliptic curves in Edwards form
- 14:15–15:00
- Cecilia Salgado, On the rank of the fibres of rational elliptic surfaces.
- 15:15–16:00
- Marius van der Put, Painlevé differential equations
- 16:15–17:00
- René Pannekoek, Parametrizations over
**Q**of cubic surfaces

### Intercity number theory seminar

15 May, Eindhoven. DIAMANT seminar room (HG 9.41)We will have coffee served in the seminar room at 11:00 and tea at 15:00.

- 11:15–12:15
- Ben Kane, Equidistribution of Heegner points and quadratic forms
- 13:00–13:55
- Ted Chinburg, Lifts of group actions on curves from characteristic p to characteristic 0
- 14:05–15:00
- Ted Chinburg, Katz Gabber covers with extra automorphisms
- 15:20–16:20
- Shabnam Akhtari, Representation of integers by binary forms

### RISC/Intercity number theory seminar

20 May, Leiden. Room 174.This extra Intercity/RISC seminar on a

**wednesday**will feature talks by the Kloosterman professor Ted Chinburg, Gabriele Dalla Torre, and Chaoping Xing.

- 11:30–12:30
- Gabriele Dalla Torre, The unit-residue group of an algebraic number field
- 13:20–14:15
- Ted Chinburg, Deformations of complexes of modules for a profinite group
- 14:25–15:20
- Ted Chinburg, Rationality of Euler characteristics
- 15:30–16:25
- Chaoping Xing, Construction of algebraic curves over finite fields from linear codes and vice versa

### Intercity number theory seminar

12 June, Nijmegen. room HG00.307 (Huygens Gebouw), Heyendaalseweg 135- 13:00–14:00
- Sander Zwegers, Mock modular forms: an introduction
- 14:30–15:30
- Oliver Lorscheid, Toroidal Eisenstein series and double Dirichlet series
- 16:00–17:00
- Dimitar Jetchev, Global divisibility of Heegner points and Tamagawa numbers

### Intercity Number Theory Seminar at the Woudschoten conference on automorphic forms.

19 June, Woudschoten. See the conference webpage.
Speakers:

10-11 Henryk Iwaniec (Rutgers): Some features of spectral summation formulas

11-12 Akshay Venkatesh (Stanford): Torsion in homology of arithmetic groups

12-13 Lunch

13-14 Emmanuel Kowalski (ETHZ): Families of Cusp Forms and L-functions

### Intercity number theory seminar

4 September, Leiden. Room 402- René Schoof,
*p*-adic representations and (φ, Γ)-modules - 14:00–15:00
- Jan-Hendrik Evertse, Complexity of algebraic numbers
- 15:15–16:15
- Hendrik Lenstra, Finding the ring of integers in a number field

### Intercity number theory seminar

18 September, Eindhoven.- René Schoof, Curves over finite fields
- 12:15–13:00
- Ronald van Luijk, Unfaking the fake Selmer group
- 14:00–14:45
- David Freeman, Pairing-friendly hyperelliptic curves and Weil restriction
- 15:00–15:45
- Bart de Smit, The valuation criterion for normal bases

### Intercity number theory seminar

30 October, CWI Amsterdam. Joint session with the RISC seminar in the Turing-zaal (the main auditorium on the ground floor, to the left of the main entrance).- Christine Bachoc, Secure Message Transmission with Small Public Discussion
- 11:30–12:30
- Andries Brouwer, The eigenvalues of the graph on the flags of a finite building, joined when in mutual general position.
- 13:30–14:30
- Heng Huat Chan, Class invariants
- 16:00–17:00
- Ronald Cramer, Towers of Algebraic Function Fields in Secure Computation

### Intercity number theory seminar

13 November, Groningen. The first lecture is in room 105 Bernoulliborg, the second in Room 5116.0116 in the Physics & Chemistry NCC Building, and the last two in room 267 Bernoulliborg.(The last two talks have been switched after the email announcement.)

- 11:45–12:45
- Marios Magioladitis, The discrete logarithm problem on isogenous hyperelliptic curves of genus 2
- 13:30–14:30
- Jaap Top, Ruled quartic surfaces
- 15:00–16:00
- Robin de Jong, Logarithmic equidistribution of division points on superelliptic curves
- 16:05–17:05
- Jorge Mozo Fernández, Results on analytic classification of germs of holomorphic foliations

### Intercity number theory seminar

4 December, Utrecht. Room 505 of the BBL building.Tentative list of speakers: Jeroen Sijsling, Jonathan Reynolds, Marco Streng, Gunther Cornelissen

- 11:30–12:20
- Jonathan Reynolds, Power integral points on elliptic curves.
- 13:30–14:20
- Jeroen Sijsling, Equations for (1;e)-curves
- 14:30–15:20
- Marco Streng, Abelian surfaces admitting an (
*l*,*l*)-endomorphism - 15:40–16:30
- Gunther Cornelissen, Arithmetic equivalence for function fields