Past events
Workshops and conferences
A symposium organised on 6-7 November 2025, by the UGC and the Utrecht Mathematical Institute, to celebrate the career and contributions of Professor Emeritus Frans Oort, on the occassion of his 90th birthday.
The workshop took place in Utrecht University on the days 14-15 May 2025. It focused on moduli of objects in abelian categories of low dimension, namely quiver representations, sheaves and Higgs sheaves on curves and surfaces. The goal was to highlight the similarities in the study of these moduli problems, and the role of mirror symmetry and S-duality in this context. The schedule, speakers and abstracts can be found on the conference website.
The workhop took place on 27-30 January 2025. The schedule, speakers and abstracts can be found on the conference website.
In May 2026, the latest meeting of the seminar took place at the University of Amsterdam with the following speakers:
| 13:30-14:30 | Jochen Heinloth (Univ. Duisburg-Essen) | On the moment measure conjecture |
| 15:00-16:00 | Julia Schneider (CNRS/Univ. Bourgogne) | Canonical semi-orthogonal decompositions for derived categories of G-surfaces |
| 16:30-17:30 | Olivier Wittenberg (Univ. Sorbonne Paris Nord) | Tight approximation for rationally simply connected varieties |
For more information about previous seminars please visit their page (outside the UU).
Guest lectures
Guest lecture by Taro Kimura (Dijon). Time: 23 October 2025 - 11:00-12:00, Hans Freudenthal Building 7.07.
Abstract: Many examples of enumerative invariants appearing in the context of algebraic geometry are given by integrating over the moduli space of maps, sheaves, and so on. When there exists a nice group action on it, we may compute such invariants based on the fixed point contributions, i.e., the equivariant localization formula. In this talk, I'd like to explain an alternative use of the localization formula based on the Jeffrey-Kirwan residue formula for multi-variable contour integrals. The key idea is to use the residue of the poles appearing in the integral to classify and evaluate the fixed point contribution under the equivariant action. I'll demonstrate this formalism with several examples, including the equivariant DT/PT invariants for the affine spaces C^3 and C^4.
Guest lecture by Balázs Szendröi (Vienna). Monday Oct 6, 13:30-14:30, HFG7.07.
Abstract: The coinvariant algebra, the quotient of the coordinate ring of (A^1)^n=A^n by the ideal generated by positive degree invariant polynomials, plays a basic role in algebraic combinatorics and the representation theory of the symmetric group S_n, equipping its regular representation with a graded algebra structure. Using the coordinate ring of (P^1)^n in its Segre embedding, I will introduce a degeneration of the coinvariant algebra, the projective coinvariant algebra, which gives a bigraded structure on the regular representation of S_n with interesting Frobenius character that generalises a classical result of Lusztig and Stanley. I will also show how this algebra contains bigraded versions of partial coinvariant algebras, coming from coordinate rings of all possible Segre embeddings. Relations to Haiman's diagonal coinvariant algebra, and a certain equivariant Hilbert scheme, will also be discussed.
A guest lecture series by Olivier de Gaay Fortman on his recent breakthrough results on failure of the integral Hodge conjecture for abelian varieties (and failure of stable rationality of the very general cubic threefold).
Guest lecture by Jan Manschot, Professor of Theoretical Physics at Trinity College Dublin. Time: 27 October 2025.
Abstract: I will discuss invariants of moduli spaces of instantons on a four-manifold, and their relation to topologically twisted Yang-Mills theory. After reviewing general aspects, I will explain recent work on Segre invariants and K-theoretic Donaldson invariants, and the physical theories whose correlations functions capture these invariants.
To prepare for the lecture and get to know more of his work, many resources are available on his webpage.
Former Seminars
A weekly seminar exploring the basics of Derived Algebraic Geometry, Vertex algebras and wallcrossing along the way. No expert knowledge was assumed from the audience or speakers. The seminar applied the techniques in Arkadij Bojko's recent work to some simple examples where wallcrossing techniques have not been applied yet. In the talks, we focus on applying the results rather than understanding their proofs, unless it carries a particular insightful idea that explains how the result can be applied.
The seminar was organised by Tom Manopulo.
See also, the event webpage
A reading seminar series aiming to understand the paper Geometric Manin's conjecture and rational curves by Lehmann and Tanimoto.
The seminar was organised by Marta Pieropan.
For more information view the seminar's website.
Titles and abstracts of talks given during the period 2021-2024 can be found in the webpage of former postdoc Woonam Lim.