On May 29, 2026, the next meeting of the Belgian-Dutch Algebraic Geometry seminar will be held at the University of Amsterdam. The lectures will be given in room D1.111 at Science Park 904.
Programme (click a title to show/hide the abstract) |
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| 13:30-14:30 | Jochen Heinloth (Univ. Duisburg-Essen) | On the moment measure conjecture
Abstract: Stability conditions help to cut out subspaces of a moduli problem that admit proper moduli spaces. In many cases these stability conditions are in the end determined by the datum of a (Chern class) of a line bundle on the moduli problem. This lead to many of the classical notions of
'semistability'.
By now we also have rather explicit geometric criteria that decide whether
an open part of a moduli problem admits a proper quotient or not. One might
therefore wonder whether the classical notions of semistability exhaust all
such open parts and it turns out that this is not the case.
The moment measure conjecture Bialynicki-Birula and Sommese gave a
conjecturally complete classification in the explict case of quotients of
torus actions. For these they found examples that cannot be constructed
through the classical method of GIT. I would like to explain how this
conjecture can be understood by looking at other cohomological degrees of
the corresponding quotient stack. (This is joint work with X. Zhang.)
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| 15:00-16:00 | Julia Schneider (CNRS/Univ. Bourgogne) | Canonical semi-orthogonal decompositions for derived categories of G-surfaces
Abstract: In this talk, I discuss a joint work with Alexey Elagin and Evgeny Shinder that lies at the intersection of birational and derived geometry. What kind of geometric information is encoded in the derived category of a variety, and how does this information behave under birational maps? We consider the case of surfaces equipped with a group action, and show that their derived categories admit a canonical (mutation-equivalence class of) semi-orthogonal decomposition that 'behaves well' with respect to birational geometry. We call such decompositions 'atomic'. If time permits, I will discuss applications to (bi-)rationality questions.
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| 16:30-17:30 | Olivier Wittenberg (Univ. Sorbonne Paris Nord) | Tight approximation for rationally simply connected varieties
Abstract: In 1885, Runge showed that holomorphic functions on an open subset of the Riemann sphere can be approximated, for the compact-open topology, by rational functions. We prove that the same remains true for holomorphic maps to any smooth complex hypersurface of degree d in Pn, when n is greater than or equal to d2-1. More generally, rationally simply connected varieties defined over the function field of a complex curve satisfy the 'tight approximation property'. This is joint work with Olivier Benoist.
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October 17, 2025, at the University of Leuven |
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| Mirko Mauri (CNRS Paris) | Baily-Borel compactifications of period images and the b-semiampleness conjecture | |
| Gavril Farkas (HU Berlin) | Chen invariants of hyperplane arrangements and Koszul modules | |
| Olga Trapeznikova (IST Austria) | Decomposition of the parabolic map to the moduli of semistable bundles | |
March 21, 2025, at the University of Amsterdam |
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| John Christian Ottem (University of Oslo) | Fano varieties with torsion in the third cohomology group | |
| Susanna Zimmermann (University of Basel) | Algebraic groups acting birationally | |
| Matthew Morrow (CNRS and Orsay) | Algebraic cycles on singular varieties | |
October 25, 2024, at the University of Antwerp |
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| Marco Robalo (Jussieu) | Gluing invariants of Donaldson-Thomas type | |
| Jan-Hendrik Bruinier (Darmstadt) | The Lefschetz decomposition of special cycles on orthogonal Shimura varieties | |
| Ana Maria Botero (Bielefeld) | On the arithmetic geometry of toric varieties | |
April 26, 2024, at Utrecht University |
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| Soumya Sankar (Utrecht) | On the rationality of conic bundle threefolds | |
| Dimitri Wyss (EPFL) | Non-archimedean integration on quotients | |
| Jef Laga (Cambridge) | Ceresa cycles of Picard curves | |
October 27, 2023, at Leiden University |
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| Rahul Pandharipande (ETH Zürich) | Abelian varieties, curves, and the Hilbert scheme of points of the plane. (See here for detailed notes.) | |
| Farbod Shokrieh (Univ. of Washington) | Arakelov invariants and non-archimedean geometry | |
| Yajnaseni Dutta (Leiden University) | Birational self-maps on Hyperkähler (HK) manifolds | |
March 24, 2023, at Radboud University Nijmegen |
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| Alexander Petrov (Harvard and MPI Bonn) | Decomposability of the de Rham complex in positive characteristic | |
| Sabrina Pauli (Duisburg-Essen)) | Counting curves over an arbitrary field using tropical geometry | |
| Emanuele Macrì (Orsay) | Hyper-Kähler manifolds and Lagrangian fibrations | |
December 9, 2022, at the University of Amsterdam |
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| Piotr Achinger (IMPAN) | The Riemann-Hilbert correspondence for rigid spaces | |
| Laura Pertusi (Milan) | Moduli spaces of stable objects in Enriques categories | |
| Dustin Clausen (Copenhagen) | Algebraic geometry from the solid perspective | |
September 30, 2022, at the KU Leuven |
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| Javier de Bobadilla (BCAM) | Monodromy at radius zero and equimultiplicity of families with constant Milnor number | |
| Valentijn Karemaker (Utrecht) | The Gauss problem for central leaves | |
| Gebhard Martin (Bonn) | On the non-degeneracy of Enriques surfaces | |
November 8, 2019, at the University of Antwerp |
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| Lie Fu (Lyon and Nijmegen) | Orbifold products on motivic cohomology and hyper-Kaehler resolution conjectures | |
| Špela Špenko (UL Bruxelles) | Perverse schobers in geometric invariant theory | |
| Stefan Kebekus (Freiburg) | Extension Theorems for differential forms and applications | |
June 21, 2019, at the University of Amsterdam |
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| Diletta Martinelli (Edinburgh) | On the geometry of contractions of the Moduli Space of sheaves of a K3 surface | |
| Zsolt Patakfalvi (EPFL) | On the Beauville-Bogomolov decomposition in positive characteristic | |
| Yichao Tian (Strasbourg) | Geometry of unitary Shimura varieties at non-quasi-split primes and arithmetic applications | |
February 1, 2019, at Utrecht University |
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| Dan Petersen (Stockholm University) | Tautological classes with twisted coefficients | |
| Donatella Iacono (Università di Bari) | DG-Lie algebras and deformation of pairs | |
| Georg Oberdieck (University of Bonn) | Quantum cohomology of the Hilbert scheme of pairs | |
September 20 and 21, 2018 at Radboud University Nijmegen |
Ching-Li Chai (UPenn) | Sustained p-divisible groups and the foliation on moduli spaces of abelian varieties |
| Jörg Wildeshaus (Paris 13) | Weights and conservativity | |
| Kestutis Cesnavicius (CNRS/Paris-Sud) | Purity for the Brauer group | |
| Claire Voisin (Collège de France) | Gonality and zero-cycles of abelian varieties | |
| Victoria Hoskins (FU Berlin) | On the motive of the stack of vector bundles on a curve | |
| Richard Thomas (Imperial College) | Refined Vafa-Witten invariants for projective surfaces | |
| Piotr Achinger (IMPAN, Warsaw) | Serre-Tate theory for Calabi-Yau varieties | |
June 8, 2018 at the KU Leuven |
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| Arend Bayer (Edinburgh) | Families of Hyperkaehler varieties via families of stability conditions | |
| Christian Liedtke (Technische Universität München) | A Néron-Ogg-Shafarevich criterion for K3 Surfaces | |
| José Burgos Gil (ICMAT, Madrid) | Grothendieck's period conjecture and zeta values | |
March 23, 2018 at Leiden University |
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| Videos of the lectures are available via youtube. | ||
| Florian Ivorra (FRIAS, Freiburg) | Quasi-unipotent motives | |
| Peter Jossen (ETH Zürich) | Galois groups and Motivic Fundamental groups | |
| Lionel Darondeau (KU Leuven) | Jet differentials and hyperbolicity | |
December 15, 2017 at Radboud University Nijmegen |
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| Johannes Nicaise (Imperial College and Leuven) | Specialization of (stable) rationality in families with mild singularities | |
| Javier Fresán (École Polytechnique) | Exponential motives | |
| Michael Groechenig (FU Berlin) | p-adic integration for the Hitchin system | |
December 9, 2016 at the University of Amsterdam |
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| June Huh (Princeton) | Enumeration of points, lines, planes, etc. | |
| Dieter Kotschick (München) and Stefan Schreieder (Bonn) | The Hodge ring of Kähler manifolds | |
| Bhargav Bhatt (Ann Arbor) | Derived splinters in mixed characteristic | |
April 22, 2016 at KU Leuven |
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| Sho Tanimoto (Copenhagen) | Towards a refinement of Manin's conjecture | |
| John Christian Ottem (Oslo) | Effective cones of cycles on blow-ups of projective space | |
| Bruno Chiarellotto (Padova) | Monodromy action and special fiber for semistable schemes over a DVR | |
December 11, 2015 at Leiden University |
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| David Holmes (Leiden) | Models of degenerating jacobians | |
| Clément Dupont (MPIM Bonn) | Motives of bi-arrangements | |
| Misha Verbitsky (ULB, Bruxelles) | Transcendental Hodge algebra | |
June 11 and 12, 2015 in Nijmegen, joint with NoGAGS |
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| Daniel Greb (Duisburg-Essen) | Movable curves and semistable sheaves | |
| Klaus Künnemann (Regensburg) | A tropical approach to non-archimedean Arakelov geometry | |
| Kevin Buzzard (Imperial College) | Pre-adic spaces and adic spaces | |
| Tim Dokchitser (Bristol) | Local arithmetic of hyperelliptic curves | |
| David Rydh (KTH Stockholm) | The local structure of Artin stacks | |
| Lars Kindler (FU Berlin) | Ramification theory for D-modules in positive characteristic | |
| Christian Lehn (Hannover) | Rational curves on singular cubic fourfolds | |
| Ulf Kühn (Hamburg) | A geometric approach to constructing elements of K2 of curves | |
November 14, 2014 at the University of Amsterdam |
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| Minhyong Kim (Oxford) | Non-abelian reciprocity laws and Diophantine geometry | |
| Mingmin Shen (UvA) | Multiplicative Chow-Künneth decompositions | |
| Jakob Stix (Frankfurt) | Gorenstein orders and abelian varieties over finite fields | |
May 16, 2014 in Leuven |
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| Olivier Benoist (Strasbourg) | Complete families of smooth space curves | |
| Frank-Olaf Schreyer (Saarbrücken) | Matrix factorizations and families of curves of genus 15 | |
| Carel Faber (Utrecht) | On the cohomology of the moduli spaces of pointed curves of genus three | |
November 22, 2013 in Nijmegen |
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| Nero Budur (Leuven) | Cohomology jump loci | |
| Stefan Schröer (Düsseldorf) | Wild quotient surface singularities | |
| René Schoof (Rome) | Finite group schemes and abelian varieties with good reduction outside one prime | |
June 14, 2013 in Leiden |
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| Walter Gubler (Regensburg) | Normal toric varieties over valuation rings of rank 1 | |
| Gaël Rémond (Bordeaux) | Isogenies and polarizations | |
| Jean-Benoît Bost (Orsay) | Pluripotential theory, heights, and algebraization on arithmetic threefolds | |
| José Ignacio Burgos Gil (ICMAT Madrid) | The singularities of the invariant metric of the sheaf of Jacobi forms on the universal elliptic curve | |
April 19, 2013 in Leuven |
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| Alejandro Soto (Regensburg) | Toric Varieties over a Valuation Ring | |
| Sébastien Boucksom (Jussieu) | A uniform version of Izumi's theorem | |
| Ariyan Javanpeykar (Leiden) | Bounds for Arakelov invariants - algorithmic and Diophantine applications | |
December 7, 2012 at the UvA |
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| Andrei Caldararu (Wisconsin) | Derived intersections | |
| Eduard Looijenga (Utrecht) | Cohomological dimension of moduli spaces of curves | |
| Daniel Huybrechts (Bonn) | Cycles on K3 surfaces | |
June 15, 2012 in Leuven |
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| Ted Chinburg (UPenn) | Small generators for S-arithmetic groups | |
| Matthieu Romagny (Jussieu) | Models of groups schemes of roots of unity | |
| Mircea Mustaţă (Michigan) | Adjoint line bundles in positive characteristic | |