
Groningen, February 7 2003
Van der Waerden Centennial Celebration
B.L. van der Waerden (2 February 1903  12 January 1996) got his PhD
degree at the university of Amsterdam in 1926 supervised by Hk. de
Vries. He was a geometry professor at the university of Groningen
from 1928 until 1931 and after that at the university of Leipzig. From
1948 till 1951 he was professor of pure and applied mathematics at the
university of Amsterdam.
After this he accepted a chair
at the university of Zürich where he remained for the rest of his
life.
On Friday, February 7th, 2003, the Dutch mathematical community
honours B.L. van der Waerden with a day of lectures
in the Academiegebouw
of the Rijksuniversiteit Groningen.
The building is located at Broerstraat 5
[map],
which can be reached by taking bus 3 or 11 from the Centraal Station
to the Grote Markt, or by a 10 minute walk.
Program

11:0011:30

Arrival and coffee

11:3012:00

Y. Dold,
Introduction

12:0013:00

H.J.M. Bos,
Descartes, Geometry and Algebra: a Twisted Tale of
Failure and Success

13:0013:45

Lunch

13:4514:45

K. Buzzard,
Classical and 2adic modular forms

14:4515:45

N. Schappacher,
Bartel van der Waerden in the thirties and
fourties:
projects and writings in algebraic geometry and in the history of
mathematics

15:4516:15

Tea

16:1517:15

T.A. Springer,
Van der Waerden and the Foundations of Algebraic
Geometry

17:1518:30

Reception



If you are interested in joining the speakers for dinner
please use our online registration form.
The dinner will most likely take place in the
Mexican restaurant Four
Roses and will cost about 30 euros.

February 21

Leiden, room 407

11:3012:30

Peter Stevenhagen,
Principal moduli and class fields 
13:3014:20

Francesco Pappalardi,
Average LangTrotter Conjecture for inerts in imaginary quadratic fields

14:3015:20

Ariane Mezard,
Deformations of wildly ramified covers

15:3016:20

Jasper Scholten,
Restriction of scalars and the discrete logarithm problem on elliptic
curves


March 7

Utrecht, room K11

11:4012:30

Frits Beukers,
Integral points on curves.

13:3014:20

Adriaan Herremans,
Arithmetic with modular symbols II

14:3015:20

Bas Edixhoven,
Twodimensional Galois representations, Hecke algebras and mod p parabolic cohomology

15:3016:20

Gabor Wiese,
Computations of weight 1 modular forms over finite fields


April 11

Leiden, room 412. Local organiser: Bas
Edixhoven

11:3012:30

Bas Edixhoven (Leiden),
On the computation of the field of definition of torsion points on
jacobians.
Abstract:
I will explain a strategy for efficiently computing the field of
definition of a torsion point of the jacobian variety of a curve over
a
number field. An interesting (and motivating) example is the ltorsion
of
the jacobian of the modular curve X_1(l), in which there is a
twodimensional Z/lZsubspace that gives the mod l Galois
representation
associated to the modular form Delta. The strategy depends on a height
estimate that still needs to be worked out. I will show how such a
height
estimate is proved in the function field case.

13:3014:30

Layla Pharamond (Paris),
The real geometry of dessins d'enfants
Abstract:
The aim of this talk is first to give a general idea of what is a
dessin
d'enfant according to Grothendieck and then to describe what I call
the
real geometry of such a dessin d'enfant, i.e., the algebraic
structure of
the preimage of the real projective line under the covering associated
to
the dessin d'enfant in terms of its combinatorial data.

14:4515:45

Stefan Wewers (Bonn),
Three point covers with bad reduction and padic uniformization
Abstract:
We study three point covers f:Y>P^1 of the projective line (i.e.
dessins
d'enfants) with bad reduction to characteristic p. For instance, we
prove:
Thm: If p strictly divides the order of the monodromy group of f then
the
field of moduli of f is at most tamely ramified at p.
The proof of this theorem relies on an analysis of the stable
reduction of
f. I will try to explain the idea of the proof and to relate it to
padic
uniformization of hyperbolically ordinary curves, introduced by
Mochizuki.

16:0017:00

Irene Bouw (Essen),
Reduction of modular curves
(joint work with Stefan Wewers)
Abstract:
In this talk I give a new proof of the stable reduction of the modular
curve X(p) to characteristic p, due to Deligne and Rapoport. The proof
does not use the fact that modular curves are moduli spaces, but
instead
uses Raynaud's results on the stable reduction of Galois covers of
curves.
More generally, one obtains an explicit formula for the number of
PSL_2(p)Galois covers of the projective lines branched at three
points
which have bad reduction to characteristic p.


May 16

Groningen, room RC255

11:3012:30

Robert Carls,
A generalized arithmetic geometric mean

13:3014:30

Lenny Taelman,
Dieudonne determinants over skew polynomial rings
[abstract+paper
]

14:4515:45

Marius van der Put,
Drinfeld modules and Krichever modules

16:0016:45

Jaap Top,
Dynamical systems and binary digits of pi,
after Bailey and Crandall
[PDF]

16:45
 Borrel


June 6

Nijmegen, collegezaal N7 (=room N1004), on the first floor of the N1
wing
Route description:
From the station Nijmegen Heyendaal, cross the big street (Heyendaalse
weg) as soon as possible. Now go right towards the university, but as
soon as there is a door in the barrier on your left, go through this
door. Now follow the main road (at the beginning perpendicular to the
Heyendaalse weg) until you reach the back of the main faculty
building. Enter the building, turn left and follow the corridor until
you reach the three elevators. Now go one floor up. Lecture hall N7
is in the corridor on your left.
Due to construction parking is limited.
See map.

13:4514:30

Reinier Bröker (Leiden),
How to construct an elliptic curve with exactly 261424513284460 (=[pi^29]) points
Abstract.
One way to construct an elliptic curve with a given number N of points
is to simply look for a prime p near N and write down curves over F_p
until you've found one with N points. This idea is perfectly sound,
but rather unattractive from a computational point of view. Another
approach proceeds by computing a minimal polynomial for the Hilbert
class field of an imaginary quadratic field of the `right'
discriminant. A popular means of doing this is by approximating values
of the jfunction that occur as the roots of the polynomial and
compute the polynomial from this data. If one tries to do this complex
analytically, one runs into the problem of rounding errors. This leads
to the question whether the same computation can be done padically.
In this talk I will first briefly recall how the complex analytic
approach works and then I will describe an algorithm that works
padically.

14:4515:30

Henk Barendregt (Nijmegen),
The challenge of computer mathematics

16:0016:45
 Freek Wiedijk (Nijmegen),
John Harrison's formalization of the AgrawalKayalSaxena primality
test
Abstract.
This talk will present work of John Harrison, as a showcase
of what formalization of elementary number theory can
look like. The work that will be shown is a formalization
in the HOL Light system of the proof of theorem 2.3 from
Bernstein's "proving primality after AgrawalKayalSaxena".
The talk will explain the foundations of HOL Light, then it
will present various examples of how mathematical notions can
be defined inside this system, and finally it will show the
AKS formalization, discussing one of the files in some detail
and then focusing within this file on one of its lemmas.


September 12

Leiden, room 412

12:1013:00

Tommy Bülow,
The Negative Pell Equation and Relative Norms of Units 
14:0014:50

Jeanine Daems,
A cyclotomic proof of Catalan's conjecture

15:0015:50

Bas Jansen,
Mersenne primes and Woltman's question

16:0016:50

Joe Buhler,
Polynomials over local fields


October 17

Nijmegen, Room N4 (N3045). On the current map of campus the talks are in building N2, but
you can only enter the building in N1.

13:1014:00

Wieb Bosma,
On primes h*3^{k}+1,
reciprocity, and residue covers

14:1015:00

Orsola Tommasi,
The rational cohomology of the moduli space of genus 4 curves

15:3016:20

Willem Jan Palenstijn,
Galois groups of radical extensions of fields

16:3017:20

Bart de Smit,
Artin Schreier theory of ramification groups


October 31

Groningen, room RC 255.

11:3012:20

M. Reversat,
Relations between modular forms and
automorphic forms in positive characteristic

12:2012:50
 Lunch

12:5013:40

J. Van Geel,
Density theorems for polynomials over finite
fields (after B. Poonen)

13:5014:40

G. Böckle,
Uniformization of Anderson tmodules

15:4516:00

GertJan van der Heiden,
lekenpraatje

16:00

PhD thesis defense of
GertJan van der Heiden

The talk and thesis defense of GertJan van der Heiden
will take place in the
Academiegebouw
of the Rijksuniversiteit Groningen.
This building is located at Broerstraat 5
[map],
which can be reached by taking bus 3 or 11 from the Centraal
Station
to the Grote Markt, or by a 10 minute walk.
The talks before 15:00 are on campus.

November 14

Universiteit van Amsterdam, the first talk in room P.227, the others in P.018.

11:3012:30

Karim Belabas,
On the 3rank of Q(p^{1/2})
Abstract:
The main result of this talk is the following statement: there exists
a positive density of primes p, such that the ideal class group
of the real quadratic field Q(p^{1/2}) has no elements of order 3. Since class
groups of such fields have no 2torsion either, this is a weak version
of Gauss's conjecture stating that infinitely many of these fields
have class number one. The result is obtained by combining sieve
methods with the theory of Delone, Faddeev, Davenport and Heilbronn,
which parametrizes cubic orders by classes of integral binary cubic
forms modulo GL(2,Z).

12:3013:30
 Lunch

13:3014:30

Hendrik Lenstra,
What is the logarithmic class group?
Abstract:
The logarithmic class group can be viewed as a Galoistheoretic
analogue for number fields of the group of rational points on the
Jacobian of a curve over a finite field. The present lecture,
which is of a tutorial nature, will provide an easily
comprehensible definition of the logarithmic class group of a
number field, as well as an "internal" description that can be
used for computational purposes.

14:4515:45

Frans Oort,
Special points on Shimura varieties, an introduction
Abstract: We formulate the AndréOort conjecture for the
moduli space of
abelian varieties, we discuss the analogy with the ManinMumford
conjecture, the connection with a conjecture by Coleman, and
we describe a series of examples.
Notes [PS] are available from the
speaker.

16:0017:00

Ben Moonen,
Introduction to Shimura varieties, I: MumfordTate groups

The last two talks form the first of three preparatory sessions
for the workshop
Special Points in Shimura Varieties, which will take place at the
Lorentz Center in Leiden in
the period december 1519.

November 28

Universiteit Leiden, room 413.

11:3012:30

Karma Dajani,
From A. Oppenheim to M. Ratner via flows on homogeneous spaces
Abstract:
It is often profitable to reformulate and generalize a conjecture from
one field in mathematics to another field. An example of this is
given by the Oppenheim's conjecture in number theory which was
generalized by Raghunathan in the 1980's to a conjecture on orbit
closures of unipotent actions on homogeneous spaces. The conjecture
lead to several new conjectures, which were all proved by Marina
Ratner in the 1990's. In this talk we will outline this historical
path, and explain the underlying ergodic theory of flows on
homogeneous spaces.

12:3013:30
 Lunch

13:3014:30

Ben Moonen,
Introduction to Shimura varieties, II: Variation of Hodge structures

14:4515:45

Christiaan van de Woestijne
Solving equations over finite fields 
16:0017:00

Johan Bosman,
Mahler's measure and special values of Lfunctions.
Abstract:
If P is a polynomial in several variables, then we define its
(logarithmic) Mahler measure m(P) as the logarithm of the geometric
mean of P over the ntorus T^{n},
where T is the unit circle in the
complex plane. David Boyd did a numerical investigation to several
families of polynomials in 2 variables and he discovered that m(P)
appears very often to be a rational multiple of a special value of an
Lseries of either an elliptic curve or a Dirichlet character. In this
talk we will examine a family of polynomials whose zero locus is
generically a curve of genus 2 and give a proof of some identities
that Boyd conjectured.

The first two talks form the second of three preparatory sessions
for the workshop
Special Points in Shimura Varieties, which will take place at the
Lorentz Center in Leiden in
the period december 1519.

December 12

Morning program:
EIDMACWI Workshop
on Factoring Large Numbers at
La Vie
with lectures by Arjen Lenstra and by Willi Geiselmann
and Rainer Steinwandt. To attend the morning program, please notify
Herman te Riele by email at herman@cwi.nl.
Afternoon program: Universiteit Utrecht,
Minnaertgebouw room 211.

14:3015:30

Ben Moonen,
Introduction to Shimura varieties, III: Basic properties of Shimura
varieties

16:0017:00

Bas Edixhoven
Galois action on special points

The last two talks form the third and last preparatory session
for the workshop
Special Points in Shimura Varieties, which will take place at the
Lorentz Center in Leiden in
the period december 1519.


