Zegel    Mathematical Institute Newsletter
May 2002
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Toren Academiegebouw

         The Mathematical Institute newsletter is maintained by Jan-Hendrik Evertse. The newsletter will be 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").

The next newsletter will cover June, July and August, since there will be no issues of the newsletter in July and August. Copy for this newsletter, such as announcements, personal notes, visits to conferences, guests, lectures of general interest, should be sent by e-mail to evertse@math.leidenuniv.nl before May 27. To avoid any inconvenient translating or typing work, copy should be submitted in English plaintext.

Agenda and announcements

  • Geachte collega's en studenten,
    De picknicktafels in de daktuin grenzend aan de kantine zijn gezamenlijk aangeschaft door I-groep, Liacs en Mathematisch Instituut.
    Deze tafels vormen een eerste en tastbare stap in een plan om de ambiance van ons I-gebouw te verbeteren. Intussen heeft het bureau Vastgoed van de universiteit architecten aangesteld die werken aan een concept-verbeteringsplan voor het I-gebouw (verkeersruimten, openbare ruimten en leslokalen).
    Op lokaal niveau wordt door de gebruikers overlegd hoe zij zelf iets kunnen verbeteren aan hun werkomgeving. De picknicktafels zijn een resultaat van dit overleg.
    Het gebruikerscomite bestaat uit: Petra Slabber (I-group), Herbert Bos (LIACS), Erwin van Soest (LIACS), Aldine Aaten (wiskunde) en Chris Zaal (wiskunde).
    Uw verbeteringsvoorstellen kunt u bij deze personen kwijt. Ook kunt u alvast nadenken over een nieuwe naam voor het gebouw, dat bij gebrek aan een betere naam tegenwoordig "I-gebouw" heet.
    Met vriendelijke groeten,
    Chris Zaal, kamer 208, tel. 071-527 7121, e-mail zaal@math.leidenuniv.nl

    Dear colleagues,
    Thanks to a combined effort of I-group, LIACS (computer science) and the Mathematical Institute, the inner garden has been supplied with some new picknick tables. It is a first step of a bigger plan aimed at redecorating the building we live in. The university real estate office has hired some architects, who will make a concept for improving the interior of our building (thoroughfare rooms, public rooms, lecture halls, etc.).
    Further, there is a users' committee, consisting of Petra Slabber (I-group), Herbert Bos (LIACS), Erwin van Soest (LIACS), Aldine Aaten (MI), Chris Zaal (MI), which is deliberating about improving our working environment and which is collecting suggestions from local users. This has already resulted in the picknick tables mentioned above. If you have any further suggestions, please let us know!
    Yours sincerely,
    Chris Zaal, room no. 208, phone 7121, e-mail zaal@math.leidenuniv.nl

  • Seminarium Recreatieve Wiskunde
    May 16: Henk van der Vorst (UU): Hoe schrijf ik een veelgeciteerd artikel
    June 6: Albert van der Schoot (UvA, Dept. of humanities): De gulden snede als esthestisch ideaal: een uitvinding van de Romantiek
    Both lectures are from 4:00-5:00 pm in room 174.

  • Starting from April 1, 2002, Peter de Kler has succeeded Janny Korevaar as P&O advisor for the Mathematical Institute.

Personal notes

  • Dr. V. Rottschäfer (formerly post-doc) is per May 1, 2002 a KNAW-fellow with Prof.dr S. Verduyn Lunel

  • New employees

    • Ph.D. Students

      Drs. J.J. Goeman per September 1, 2001 with Prof.dr. S.A. van de Geer and Prof.dr. J.C. van Houwelingen (Department of Medicine)

      Drs. S. Aparicio per January 1, 2002 with Prof.dr. G. van Dijk
      I'm Sofia Aparicio and I come from Zaragoza, Spain (between Madrid and Barcelona, very close to the Pirineos, beautiful mountains!! :-) I arrived in the Netherlands on January 7th to make my Ph.D. with Professor van Dijk, in Lie Groups. Before I came here, I was an Erasmus student in Naples, Italy, an experience that I liked very much. Apart from Mathematics, I like lots of things like music, cinema, to dance, sport activities (I am beginning to practice aerobics and yoga in the sportcentrum!), but my favourite one is to travel, to know other countries, other cultures... Finally, I would like to say that I'm very happy to stay here. I like a lot Holland!!!

      Groetjes, SOFIA

      Drs. L. Ferracina per March 1, 2002 with Prof.dr. M.N. Spijker
      Hello everybody,
      My name is Luca Ferracina. I was born in Vicenza (Italy) but I studied in Padova (where I got my University degree), a big city 80 Km from Venice. Why I'm here is a very long story. I started my Ph.D. position in Italy one year and a half ago. I had the possibility to come in Leiden for 6 months with an exchange program. I felt so happy, I worked so well with Professor Spijker that I asked him to remain. It was possible and.. I started my new Ph.D. position.. Dutch Ph.D. position! Now I'm in the numerical analysis group working on contractivity and monotonicity of Runge-Kutta methods for solving ODEs arising from semi-discretization of PDEs. I'm sorry I'm writing in English but when 7 months ago I was in Holland for the first time, I didn't speak one word in English and Dutch was too difficult for me. A Dutch letter..  it will be for the next time!

      Best regards, Luca

      Drs. R.M. Bröker per April 1, 2002 with Prof.dr. P. Stevenhagen and Dr. B. de Smit
      At April 1st, I started as a PhD student under supervision of Peter Stevenhagen and Bart de Smit. Since my Master's thesis was about Formal Groups, it is likely that my current research will head in that direction also. Like most people in the number theory group, I also live in Amsterdam; main difference is that I spent some years at the VU instead of the UvA ;-) Besides travelling by train to Leiden, it is my plan to walk to the university a few times. Since I am planning to walk the `4-daagse' of Nijmegen (4 times 50 km), this should be a good training! My less crazy hobbies include the traditional New Year's Dive and playing go (currently, I'm 9th kyu), so walk by if you're looking for a go-opponent!

      Reinier Bröker

    • Helpdesk

      R. Huizer per September 16, 2001

  • Departed
    • Dr. K. in 't Hout per April 15, 2002 (to ABN-AMRO, Amsterdam)
    • Drs. N. Popov per May 1, 2002 (to Goudse verzekeringen, Gouda)

  • Guests
    • Prof. Pingzhi Yuan (University of Xian, China) will visit our institute from May 1, 2002- March 1, 2003 to do number theoretic research with Prof. Tijdeman.


  • Propedeuse exams (August 31, 2001)
    • J.H. Bakker
    • L.M. ter Bruggen Hugenholtz
    • J.G. Dopper
    • M. van Duin
    • A.R. Hoen
    • G. Houtman
    • M.B.N. van der Meer
    • Leo van Nierop
    • J.J. Pöll
    • R. de Putter
    • M. van der Schans
    • A.C. Veldman
    • W.J.A. Wel

  • Doctoral exams (January 25, 2002)
    • M. Appel
      Master's thesis: Discrete dynamische systemen
      Supervisor: Prof.dr.ir. L.A. Peletier

    • P.M. van de Ven
      Master's thesis: Kinematics of Triaxial Galaxies: Solving the Jeans Equations
      Supervisor: Prof.dr.ir. L.A. Peletier

  • Doctoral exams (April 26, 2002)
    • H.J. Dirksen
      Master's thesis: Trends for ASR in 118 - KPN
      Supervisor: Prof.dr. S.M. Verduyn Lunel


  • Ph.D-thesis defenses
    • June 5, 2:15 pm: S.H. Cavallar: On the Number Field Sieve Integer Factorisation Algorithm.
      Promotor: Prof.dr. R. Tijdeman
      Copromotor: Dr. ir. H.J.J. te Riele (CWI)

  • Visits abroad
    • Drs. C.E. van de Woestijne:
      Semestre Groupes Lineaires Algebriques, EPFL, Lausanne, April 29-May 25
    • Dr. J.-H. Evertse, Drs. Sz. Tengely, Prof.dr. R. Tijdeman:
      Conference Problèmes Diophantiens, CIRM, Luminy, France, May 6-10

  • Technical reports July-December 2001
         MI 2001-11   Guido van den Heuvel: Cross norms in numerical analysis
    MI 2001-12 R.M. van Luijk: On Perfect Cuboids
    MI 2001-13 R.W. Ghrist, J.B. van den Berg , R.C. van der Vorst: Morse theory on spaces of braids and Lagrangian dynamics
    MI 2001-14 Rein van der Hout: On the nonexistence of finite time bubble trees in symmetric harmonic map heat flows from the disk to the 2-sphere
    MI 2001-15 Fan ding and Hansjörg Geiges: A Legendrian surgery presentation of contact 3-manifolds
    MI 2001-16 Hansjörg Geiges and Jesús Gonzalo: Moduli of Contact circles
    MI 2001-17 John Mallet-Paret and Sjoerd Verduyn Lunel: Exponential dichotomies and Wiener-Hopf factorizations for mixed-type functional differential equations
    MI 2001-18 Onno van Gaans and Jan van Neerven: Stochastic Differential Equations
    MI 2001-19 Jan-Hendrik Evertse and Roberto G. Ferretti: Diophantine inequalities on projective varieties
    MI 2001-20 J.-H. Evertse, P. Moree, C.L. Stewart and R. Tijdeman: Multivariate Diophantine equations with many solutions
    MI 2001-21 G. van Dijk: A new approach to Berezin kernels and canonical representations
    MI 2001-22 T.L. van Noorden, S.M. Verduyn Lunel and A. Bliek: The Efficient Computation of Periodic States of Cyclically Operated Chemical Processes
    MI 2001-23 Sara van de Geer: Maximum likelihood for nonparametric mixture models
    MI 2001-24 N. Saradha and R. Tijdeman: On the transcendence of infinite sums of values of rational functions
    MI 2001-25 Hansjörg Geiges and Jesús Gonzalo: Contact Spheres and Quaternionic Structures
    MI 2001-26 K.J. in 't Hout and b. Zubik-Kowal: On the stabilityof Radau IIA Collocation Processes for Delay Differential Equations
    MI 2001-27 L. Mohammadi and S. van de Geer: On more or less simple classifiers
    MI 2001-28 R.J. Simpson and R. Tijdeman: Multi-dimensional versions of a theorem of Fine and Wilf and a formula of Sylvester
    MI 2001-29 B. Gaujal, A. Hordijk and D.A. van der Laan: On orders and bounds for multimodular functions
    MI 2001-30 T.L. van Noorden, S.M. Verduyn Lunel, A. Bliek: A Broyden Rank p+1 Update Construction Method with Subspace Iteration
    MI 2001-32 Arie Hordijk and Nikolai Popov: Large deviation bounds for face-homogeneous random walks in the quarter plane

  • Technical reports January-April 2002
         MI 2002-01   Filippo Gazzola, Bert Peletier, Patricia Pucci, James Serrin: Asymptotic behavior of ground states of quasi-linear elliptic problems with two vanishing parameters, part II
    MI 2001-02 Jan-Hendrik Evertse: On resultant inequalities
    MI 2002-03 Jan-Hendrik Evertse and Roberto G. Ferretti: A variation on Siegel's lemma
    MI 2002-04 T.L. van Noorden, S.M. Verduyn Lunel, A. Bliek: Optimization of Cyclically Operated Reactors and Separators
    MI 2002-05 V.F. Molchanov: Canonical Representations and Overgroup
    MI 2002-06 V.F. Molchanov and G. van Dijk: H-invariants for the universal covering group of SL(2,R)
    MI 2002-07 Onno van Gaans: A series approach to stochastic differential equations with infinite dimensional noise
    MI 2002-08 Onno van Gaans and Sjoerd Verduyn Lunel: Long term behavior of dichotomous stochastic differential equations in Hilbert spaces
    MI 2002-09 Bart De Smit, Wieb Bosma: On arithmetically equivalent number fields of small degree

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