On April 26, 2024, the next meeting of the BelgianDutch Algebraic Geometry seminar will be held at Utrecht University. Location: Ruppert Rood (Utrecht Science Park).
Programme (click a title to show/hide the abstract) 

13:1514:15  Soumya Sankar (Utrecht)  On the rationality of conic bundle threefolds
Abstract: One of the major programs in algebraic geometry seeks to understand when a given variety is rational, and what the obstructions to rationality are. From this perspective, conic bundles are a geometrically rich class of varieties. Hassett—Tschinkel and Benoist—Wittenberg recently introduced a rationality obstruction that can be translated into a question about curve classes on threefolds. I will talk about joint work with Sarah Frei, Lena Ji, Bianca Viray and Isabel Vogt, where we study curve classes on certain conic bundle threefolds over arbitrary fields of odd characteristic. We then use the description of these classes to study the rationality of such varieties

14:4515:45  Dimitri Wyss (EPFL)  Nonarchimedean integration on quotients
Abstract: Motivated by mirror symmetry, Batyrev defines 'stringy' Hodge numbers for a variety X with Gorenstein canonical singularities using motivic integration. While in general it is an open question, whether these numbers are related to a cohomology theory, the orbifold formula shows, that if X has quotient singularities, they agree with ChenRuan's orbifold Hodge numbers.
I will explain how to generalize this orbifold formula to quotients of smooth varieties by linear algebraic groups. As an application we obtain identifications of stringy Hodge numbers with enumerative invariants, socalled BPSinvariants, in the case when X is the moduli space of a CY1 category. This is joint work with Michael Groechenig and Paul Ziegler.

16:1517:15  Jef Laga (Cambridge)  Ceresa cycles of Picard curves
Abstract: The Ceresa cycle is a canonical algebraic 1cycle in the Jacobian of a curve with a marked point. In some sense it is the simplest nontrivial canonical algebraic cycle 'beyond homology' and as such it is a natural testing ground for our knowledge of cycles on abelian varieties. The Ceresa cycle vanishes for all hyperelliptic curves, but beyond this little is known about the locus of curves in Mg where this cycle is torsion. In this talk I will discuss joint work with Ari Shnidman where we find this torsion locus for a special family of genus3 curves called Picard curves.

October 27, 2023, at Leiden University 

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 nonarchimedean geometry  
Yajnaseni Dutta (Leiden University)  Birational selfmaps on Hyperkähler (HK) manifolds  
March 24, 2023, at Radboud University Nijmegen 

Alexander Petrov (Harvard and MPI Bonn)  Decomposability of the de Rham complex in positive characteristic  
Sabrina Pauli (DuisburgEssen))  Counting curves over an arbitrary field using tropical geometry  
Emanuele Macrì (Orsay)  HyperKähler manifolds and Lagrangian fibrations  
December 9, 2022, at the University of Amsterdam 

Piotr Achinger (IMPAN)  The RiemannHilbert 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 

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 nondegeneracy of Enriques surfaces  
November 8, 2019, at the University of Antwerp 

Lie Fu (Lyon and Nijmegen)  Orbifold products on motivic cohomology and hyperKaehler 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 

Diletta Martinelli (Edinburgh)  On the geometry of contractions of the Moduli Space of sheaves of a K3 surface  
Zsolt Patakfalvi (EPFL)  On the BeauvilleBogomolov decomposition in positive characteristic  
Yichao Tian (Strasbourg)  Geometry of unitary Shimura varieties at nonquasisplit primes and arithmetic applications  
February 1, 2019, at Utrecht University 

Dan Petersen (Stockholm University)  Tautological classes with twisted coefficients  
Donatella Iacono (Università di Bari)  DGLie 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 

ChingLi Chai (UPenn)  Sustained pdivisible groups and the foliation on moduli spaces of abelian varieties  
Jörg Wildeshaus (Paris 13)  Weights and conservativity  
Kestutis Cesnavicius (CNRS/ParisSud)  Purity for the Brauer group  
Claire Voisin (Collège de France)  Gonality and zerocycles of abelian varieties  
Victoria Hoskins (FU Berlin)  On the motive of the stack of vector bundles on a curve  
Richard Thomas (Imperial College)  Refined VafaWitten invariants for projective surfaces  
Piotr Achinger (IMPAN, Warsaw)  SerreTate theory for CalabiYau varieties  
June 8, 2018 at the KU Leuven 

Arend Bayer (Edinburgh)  Families of Hyperkaehler varieties via families of stability conditions  
Christian Liedtke (Technische Universität München)  A NéronOggShafarevich criterion for K3 Surfaces  
José Burgos Gil (ICMAT, Madrid)  Grothendieck's period conjecture and zeta values  
March 23, 2018 at Leiden University 

Videos of the lectures are available via youtube.  
Florian Ivorra (FRIAS, Freiburg)  Quasiunipotent 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 

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)  padic integration for the Hitchin system  
December 9, 2016 at the University of Amsterdam 

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 

Sho Tanimoto (Copenhagen)  Towards a refinement of Manin's conjecture  
John Christian Ottem (Oslo)  Effective cones of cycles on blowups of projective space  
Bruno Chiarellotto (Padova)  Monodromy action and special fiber for semistable schemes over a DVR  
December 11, 2015 at Leiden University 

David Holmes (Leiden)  Models of degenerating jacobians  
Clément Dupont (MPIM Bonn)  Motives of biarrangements  
Misha Verbitsky (ULB, Bruxelles)  Transcendental Hodge algebra  
June 11 and 12, 2015 in Nijmegen, joint with NoGAGS 

Daniel Greb (DuisburgEssen)  Movable curves and semistable sheaves  
Klaus Künnemann (Regensburg)  A tropical approach to nonarchimedean Arakelov geometry  
Kevin Buzzard (Imperial College)  Preadic 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 Dmodules in positive characteristic  
Christian Lehn (Hannover)  Rational curves on singular cubic fourfolds  
Ulf Kühn (Hamburg)  A geometric approach to constructing elements of K_{2} of curves  
November 14, 2014 at the University of Amsterdam 

Minhyong Kim (Oxford)  Nonabelian reciprocity laws and Diophantine geometry  
Mingmin Shen (UvA)  Multiplicative ChowKünneth decompositions  
Jakob Stix (Frankfurt)  Gorenstein orders and abelian varieties over finite fields  
May 16, 2014 in Leuven 

Olivier Benoist (Strasbourg)  Complete families of smooth space curves  
FrankOlaf 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 

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 

Walter Gubler (Regensburg)  Normal toric varieties over valuation rings of rank 1  
Gaël Rémond (Bordeaux)  Isogenies and polarizations  
JeanBenoît 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 

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 

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 

Ted Chinburg (UPenn)  Small generators for Sarithmetic groups  
Matthieu Romagny (Jussieu)  Models of groups schemes of roots of unity  
Mircea Mustaţă (Michigan)  Adjoint line bundles in positive characteristic 