Joint Seminar on Complex Algebraic Geometry and Complex Analysis
(Bochum - Essen - Köln - Wuppertal)

Photo by Max Greve and Timo Bobert

The Seminar

The "Joint Seminar on Complex Algebraic Geometry and Complex Analysis" is a research seminar, organised by the algebraic and complex geometry research groups in Bochum, Essen, Cologne, and Wuppertal. The seminar meets roughly twice per semester for a full day in Bochum, Essen, Cologne, or Wuppertal. There are three talks per meeting, both by invited guests and by speakers from the organising universities. We aim to leave ample room for discussions.

The talks are open for everyone. Contact one of the organisers if you are interested in attending the meeting. We have some funds that might help to support travel for some junior participants.

Meetings of the seminar are partially supported by

  • SFB/TR 45 "Periods, moduli spaces and arithmetic of algebraic varieties"
  • SFB/TR 191 "Symplectic structures in geometry, algebra and dynamics"

Next Meeting


The next meeting will take place on Friday, July 6th, 2018 in Cologne.


  • Turgay Bayraktar (Istanbul): Random Sparse Polynomials

    It is well-known that Newton polytope of a Laurent polynomial has a crucial influence on its value distribution and in particular on its zero set. A classical result due to Bernstein-Kouchnirenko asserts that for systems of Laurent polynomials in general position the number of simultaneous zeros in the torus (\Bbb{C}^*)^m depends only on their Newton polytopes. In this talk, I will present a quantitative localization of Bernstein-Kouchnirenko Theorem. A basic tool is P-pluripotential theory which is a generalization of classical Lelong's theory in the complex Euclidean space. If time permits, I will also mention some applications regarding the asymptotic distribution of amoebas associated with Laurent polynomials.

  • Jarek Buczynski (Warsaw): Algebraic torus actions on contact Fano manifolds

    A complex manifold is a contact manifold if there is a distribution in the tangent bundle which is as non-integrable as possible. I will report on recent progress in classification of projective contact manifolds focusing on the case of (complex) dimension 7 and 9. Our work implies the classification of quaternion-Kaehler manifolds of (real) dimensions 12 and 16, a famous problem from Riemannian geometry. The tools we use include representation theory and actions of (complex) reductive groups on manifolds, symplectic geometry, characteristic classes, and equivariant localisation theorems. The talk is based mainly on "Algebraic torus actions on contact manifolds" by Jarosław A. Wiśniewski and myself, with an appendix by Andrzej Weber, which is available as arXiv:1802.05002.

  • Andrew Dancer (Oxford): Quivers, nonreductive quotients and symplectic duality

    Symplectic implosion is an abelianisation construction for group actions on symplectic spaces. There is also an analogue in hyperkahler geometry, and both the symplectic and hyperkahler implosions can be viewed as quotients by nonreductive groups. We discuss current work (with Hanany and Kirwan) on identifying symplectic duals of hyperkahler implosions.


10:30 - 11:30 Dancer

11:45 - 12:45 Bayraktar

12:45 - 14:30 Lunch break

14:30 - 15:30 Buczynski


Universität zu Köln
Mathematisches Institut

All talks will take place in Seminar Room 2 @ Mathematical Institute.

How to find the seminar room: see the map on the following website.


Kevin Fritsch
Ruhr-Universität Bochum
kevin [dot] fritsch [at] rub [dot] de

Daniel Greb
Universität Duisburg-Essen
daniel [dot] greb [at] uni-due [dot] de

George Marinescu
Universität zu Köln
gmarines [at] math [dot] uni-koeln [dot] de

Jean Ruppenthal
Bergische Universität Wuppertal
jean [dot] ruppenthal [at] math [dot] uni-wuppertal [dot]de

Past Meetings

26.4.2013, Bochum: Tim Kirschner, Christian Miebach, Henrik Seppänen

28.6.2013, Wuppertal: Rafael Andrist, Immanuel Stampfli, Matei Toma

22.11.2013, Bochum: Sébastien Boucksom, Egmont Porten, Sönke Rollenske

24.1.2014, Wuppertal: Clemens Jörder, Helge Ruddat, Jörg Winkelmann

16.5.2014, Bochum: Alberto Abbondandolo, Judith Brinkschulte, Julius Ross

20.6.2014, Wuppertal: Julie Déserti, Slawomir Dinew, Slawomir Rams

24.10.2014, Bochum: Henri Guenancia, Shulim Kaliman, Adriano Tomassini

15.12.2014, Wuppertal: Richard Lärkäng, Christian Miebach, Marco Spinaci

7.5.2015, Essen: Brent Doran, Erwan Rousseau, Emanuel Scheidegger

15.6.2015, Bochum: Roya Beheshti, Daniel Greb, Hossein Raufi

27.11.2015, Wuppertal: Francesco Bei, Kai Cieliebak, Tyson Ritter

1.2.2016, Essen: Ursula Ludwig, George Marinescu, Wenhao Ou

25.4.2016, Wuppertal: Gian Maria Dall’Ara, Christian Lehn, Luca Tasin

26.6.2016, Cologne: Chin-Yu Hsiao, Stefan Nemirovski, Nikhil Savale

25.11.2016, Bochum: Ana-Maria Brecan, Antonio di Scala, Dan Popovici

27.1.2017, Essen: Tim Kirschner, Viêt Anh Nguyên, Stefan Schreieder

21.4.2017, Wuppertal: Vicente Cortés, Philipp Naumann, Markus Reineke

7.7.2017, Cologne: Roger Bielawski, Dan Coman, Martin Schwald

3.11.2017, Bochum: Junyan Cao, Sönke Rollenske, Robert Szöke

1.2.2018, Essen: Gilberto Bini, Ruadhaí Dervan, Hendrik Herrmann

27.4.2018, Wuppertal: Hugues Auvray, Bernd Stratmann, Michael Lennox Wong

6.7.2018, Cologne: Turgay Bayraktar, Jarek Buczynski, Andrew Dancer