Mathematical Institute Newsletter
October 2005
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Toren Academiegebouw

The Mathematical Institute Newsletter is maintained by Jan-Hendrik Evertse. In general, the newsletter is issued the first week of each month, except for July and August. The electronic version of the newsletter can be found on
(go to the homepage of the Mathematical Institute and click on "Newsletter").

Copy for the next newsletter, such as announcements, personal notes, visits to conferences, guests (with place of origin and date of arrival and departure), lectures of general interest, Ph.D. thesis defenses (with title of thesis), etc. should be sent by e-mail to evertse (at before October 27. Copy should be submitted in English plaintext, so that it can be inserted into the newsletter without time consuming typing or translating work.

Agenda and announcements

  • Diamant Intercity Number Theory Seminar on Friday October 7 in Leiden

    This is a joint session with the Intercity Geometry Seminar. The seminar will be followed by Johan de Jong's Kloosterman lecture. See for further information.

  • Kloosterman lecture by Johan de Jong on Friday October 7

    Johan de Jong (Columbia University, New York, USA, specialized in algebraic geometry) has been appointed as the Kloosterman professor 2005. He is visiting our institute during October and November. On Friday October 7 he will give his Kloosterman lecture, titled Rational points and rational connectivity. This lecture is meant for a general mathematical audience. The lecture will be from 16:00-17:00 in room 312 of the Snellius.

  • General Colloquium lecture by Robin de Jong on Thursday October 20

    Title: Moduli spaces of curves.
    Time/place: 16:00-17:00, Snellius, room 174.
    The colloquium lecture is preceded by coffee and tea at 15:45 in room 174. See for further information.

  • Science Day (Wetenschapsdag) on Sunday October 23

    For further information (in Dutch) see

  • PhD defense by Sofía Aparicio Secanellas on Monday October 31

    Title thesis: Invariant Hilbert subspaces of the oscillator representation
    Promotor: Prof. Gerrit van Dijk
    Time/place: October 31, 15:15, Academiegebouw

  • ALGANT program has started

    The universities of Bordeaux, Leiden and Padova are offering a common EU-funded Master's program in algebra, geometry and number theory, called ALGANT. This program is meant for international students. Students taking part in this program are obliged to follow courses at all three participating universities. The ALGANT program has just started and at the moment there are eight ALGANT students in Leiden, from Colombia, Iran, Israel, Italy, Malaysia, Russia, Syria and Venezuela. From October 24-28 there will be an official take-off week in Bordeaux. For further information, see

  • Geometry Seminar "Cohomology of Quasi-Coherent Sheaves"

    This fall there will be a seminar on the above mentioned topic. Further information: .

  • Workshop "Dynamics of Patterns" at Lorentz Center from November 7-11

    Further information:

  • Christmas Buffet Dinner on Thursday December 15

    Further information will follow.

Doctoral exams

- Wouter Johannes van der Wel
Date: September 20
Title Master's thesis: De relatie tussen algorithmes voor het oplossen van Markovbeslissingsproblemen
Graduation committee: Dr. M.F.E. de Jeu (chairman), Prof.dr. L.C.M. Kallenberg (supervisor), Dr. F.M. Spieksma.

- Jinxia Ma
Date: September 23
Title Master's thesis: Forecast of mail volumes for sorting centers
Graduation committee: Dr. M.F.E. de Jeu (chairman), Dr. E.W. van Zwet (secretary), Dr. F.M. Spieksma, Drs. F.J. Schelhaas (TPG).

Personal notes

  • New personnel

    - Christian Svensson has started per February 1 as an AIO. He is supervised by Marcel de Jeu and Sergei Silvestrov (Lund, Sweden).

    "My name is Christian Svensson and I am a PhD student of Marcel de Jeu and Sergei Silvestrov since february 2005. I am originally from Sweden, where I did most of my undergraduate studies in Lund. I moved to Leiden permanently in August, since I spent 3 months in Antwerp attending a lecture series on non-commutative geometry, and during the beginning of the summer I worked with my co-supervisor Sergei Silvestrov in Lund, Sweden. My research is concerned with connections between dynamical systems and operator algebras. Given a classical dynamical system you can for example "build" a (non-commutative) C*-algebra and obtain certain equivalences between properties of the system and the algebra. One of the problems that arise in this context is classification of commutative subalgebras of non-commutative (operator-)algebras."

    - Dr. Fabio Mainarda has started per September 1 as a postdoc in Edixhoven's VICI project.

    "I'm Italian and I had my bachelor degree in mathematics in Rome where I started to study algebraic number theory under the direction of Prof.R. Schoof. In November 2000, I moved to Paris where I began my PhD at the University of Paris 13. My advisor was prof.J. Tilouine (and my co-advisor was E. Urban). The subject of my doctoral thesis was the application of the arithmetic theory of automorphic forms on unitary groups to classical Iwasawa theory, namely the main conjecture for CM fields. At present, I have a post-doctoral position for one year (a NWO-VICI grant) in Leiden, in the geometry group."

    - Ionica Smeets has started per September 1 as an AIO. She is supervised by Rob Tijdeman and Cor Kraaikamp (TU Delft).

    "Ionica Smeets graduated from Delft University of Technology in 2005. Her thesis "Arithmetic and ergodic approximation properties of Rosen continued fractions" was supervised by Cor Kraaikamp. In Leiden she will work as an AIO on the project "Simultaneous diophantine approximations and applications" under supervision of Rob Tijdeman, with Cor Kraaikamp as co-advisor. The goal of the project is to find new multi-dimensional continued fraction algorithms, based on the LLL-algorithm for reducing bases. A large part of the project will be dedicated to applying these algorithms to various problems from combinatorial geometry.
    Besides doing research Ionica Smeets works one day a week as the national pr-girl for mathematics. Part of her job is to write articles for popular-scientific websites such as"

    - Drs. G. Geuze has started per September 1 as LIO ("Leraar In Onderzoek", secondary school teacher doing a research project) with Peter Stevenhagen. She will work on the ABC-conjecture.

    - Drs. J. Bouw (LIO until September 1 with Peter Stevenhagen), has started per September 1 as an AIO with Peter Stevenhagen for one day a week.

    - Hendrik Verhoek has started per October 1 as a systems manager for 20 hours a week (to replace Chris Rietveld).

    - Onno W. van Gaans has been awarded a VIDI-grant by NWO. Starting January 1, 2006 he will be working at our institute in the Analysis and Stochastics group.

    - Prof.dr. Philippe P.J.E. Clement (Professor Emeritus of the Technische Universiteit Delft) will start per November 7 as a guest collaborator in the Analysis and Stochastics group.

  • Departures per September 1

    - Dr. W.B.Hart (postdoc)
    - Dr. J.F.Williams (postdoc)
    - Dr. C. Fuchs (guest)
    - Mrs. G.Hadjicharalambous M. Sc. (AIO)
    - Dr. G. Wiese (AIO)
    (to Regensburg as postdoc)
    - Drs. J.J.Goeman (AIO)

  • Departures per October 1

    - Mrs. B. Tarigan, M.Sc. (AIO) (to Zurich with Sara van de Geer)
    - Dr. L. Ferracina
    - Drs. C. van de Woestijne (AIO)
    (to the Johann Radon Institute for Applied and Computational Mathematics in Linz, this is an institute of the Austrian Academy of Sciences).


  • Guest of Rob Tijdeman:

    - Valerie Berthé (Montpellier) from October 16-21.

Visits/lectures outside our institute

- Bert Peletier: from October 17-28 he will be at Rutgers University, New Brunswick, New Jersey USA for a working visit.

- Rein van der Hout and Vivi Rottschäfer: from October 24-28 they will visit Chris Budd (University of Bath).

- Lectures on Escher and the Droste effect:
October 20: Bart de Smit at the Natuurkundig Gezelschap te Leiden
October 25: Hendrik Lenstra's Clay Public Lecture at the Clay Mathematics Institute in Cambridge, Massachusetts:;
October 29: Bart de Smit at the annual meeting of Ars et Mathesis, Baarn:
As part of our "Studiefestival" Bas Haring will interview Hendrik Lenstra about the Escher-project on October 29 in a tent next to the Pieterskerk.

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