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Spring Semester 2026

Date / Time Speaker Title Location
20 January 2026
13:00-14:00 		Dr. Denis Nesterov
ETH Zürich
Details

Algebraic Geometry and Moduli Seminar

Title Compactifications and Degenerations
Speaker, Affiliation Dr. Denis Nesterov, ETH Zürich
Date, Time 20 January 2026, 13:00-14:00
Location HG E 1.1
Abstract I will discuss a universal pattern that appears in the compactification problem for spaces parametrizing points, maps, and vector bundles associated with a complex variety. This leads to numerous interesting correspondences, shedding light on the geometry of Hilbert schemes, Hurwitz spaces, and Gieseker moduli spaces of stable sheaves.
Compactifications and Degenerationsread_more
HG E 1.1
24 January 2026
15:00-16:30 		Dr. Sam Molcho
Roma I
Details

Algebraic Geometry and Moduli Seminar

Title Intesection theory of compactifications of A_g
Speaker, Affiliation Dr. Sam Molcho, Roma I
Date, Time 24 January 2026, 15:00-16:30
Location HG G 19.1
Intesection theory of compactifications of A_g
HG G 19.1
11 March 2026
13:30-15:00 		Beatrice Bernasconi
ETH Zürich
Details

Algebraic Geometry and Moduli Seminar

Title Dynamical Sarkisov length in the plane Cremona group
Speaker, Affiliation Beatrice Bernasconi, ETH Zürich
Date, Time 11 March 2026, 13:30-15:00
Location HG G 43
Abstract We will give an overview of the Sarkisov program in higher dimension and then describe it in the case of rational surfaces. We will define the Cremona group over the projective plane and some dynamical invariants for its elements. Finally, we will look at a very special dynamical invariant, namely the Sarkisov length.
Dynamical Sarkisov length in the plane Cremona groupread_more
HG G 43
13 March 2026
16:00-17:30 		Lycka Drakengren
ETH Zürich
Details

Algebraic Geometry and Moduli Seminar

Title The Prym map near the locus of decomposable abelian varieties
Speaker, Affiliation Lycka Drakengren, ETH Zürich
Date, Time 13 March 2026, 16:00-17:30
Location HG G 43
Abstract We study the codifferential of the Prym map at the double covers of smooth curves whose Prym varieties decompose nontrivially as a product of abelian varieties, to show that the fiber product of the Prym map R_g -> A_(g-1) and the product map A_k x A_(g-1-k) -> A_(g-1) for 1 ≤ k ≤ (g-1)/2 is smooth.
The Prym map near the locus of decomposable abelian varietiesread_more
HG G 43
18 March 2026
13:30-15:00 		Dr. Gabriel Ribeiro
ETH Zürich
Details

Algebraic Geometry and Moduli Seminar

Title A moduli space of character sheaves
Speaker, Affiliation Dr. Gabriel Ribeiro, ETH Zürich
Date, Time 18 March 2026, 13:30-15:00
Location HG G 43
Abstract Let G be a connected commutative algebraic group over the complex numbers. In this talk, I will introduce a class of multiplicative line bundles with flat connection on G, called character sheaves, and describe the construction and geometry of their moduli space. These objects are inspired by ℓ-adic local systems that play a central role in modern analytic number theory. The construction of the moduli space relies on the so-called de Rham space, which provides a stack-theoretic approach to de Rham cohomology. If time permits, I will explain how the geometry of this moduli space leads to generic vanishing theorems for de Rham cohomology, and how these results give rise to a common framework for differential and difference Galois theory.
A moduli space of character sheavesread_more
HG G 43
20 March 2026
16:00-17:30 		Prof. Dr. Andrew Kresch
Universität Zürich
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Algebraic Geometry and Moduli Seminar

Title Specialization method and applications to rationality questions
Speaker, Affiliation Prof. Dr. Andrew Kresch, Universität Zürich
Date, Time 20 March 2026, 16:00-17:30
Location HG G 43
Specialization method and applications to rationality questions
HG G 43
15 April 2026
13:30-15:00 		Jeremy Feusi
ETH Zürich
Details

Algebraic Geometry and Moduli Seminar

Title Tropical geometry and computations on the moduli space of abelian varieties
Speaker, Affiliation Jeremy Feusi, ETH Zürich
Date, Time 15 April 2026, 13:30-15:00
Location HG G 43
Abstract We show how tropical geometry provides an effective tool for cohomological computations on (partial) compactifications of the moduli space of principally polarized abelian varieties. As an application, we extend the Fourier-Mukai transform to the torus rank 1 partial compactification and use it to define a weight filtration on the Chow ring of the partial compactification of the universal family. We also discuss extensions to more general toroidal compactifications, which allow us to study the moduli space of log abelian varieties and reinterpret results by Faltings-Chai.
Tropical geometry and computations on the moduli space of abelian varietiesread_more
HG G 43
17 April 2026
16:00-17:30 		Aitor Iribar López
ETH Zürich
Details

Algebraic Geometry and Moduli Seminar

Title Relations in the tautological ring of Mumford's compactification
Speaker, Affiliation Aitor Iribar López, ETH Zürich
Date, Time 17 April 2026, 16:00-17:30
Location HG G 43
Abstract On the universal family of abelian varieties, two key formulas have been known for a long time: [e] = \theta^g/g! and \theta^{g+1}=0, where $e$ is the class of the zero section and $\theta$ is the symmetric theta divisor. The moduli space of abelian varieties can be partially compactified by torus rank 1 degenerations. These are semistable families that contain a semiabelian variety. Two basic questions arise: how can we express the class of the zero section in terms of simpler "tautological" classes? What are the relations between tautological classes? We use Fourier transforms and weight decomposition to address both questions. This is a continuation of the talk on Wednesday by J. Feusi, and it is based on joint work with Y. Bae, J. Feusi and S. Molcho.
Relations in the tautological ring of Mumford's compactificationread_more
HG G 43
24 April 2026
16:00-17:30 		Prof. Dr. Andrea Brini
University of Sheffield
Details

Algebraic Geometry and Moduli Seminar

Title On the conifold gap for local P2
Speaker, Affiliation Prof. Dr. Andrea Brini, University of Sheffield
Date, Time 24 April 2026, 16:00-17:30
Location HG G 43
Abstract The `conifold gap' conjecture asserts that the polar part of the Gromov-Witten potential of a Calabi-Yau threefold near its conifold locus has a universal expression described by the logarithm of the Barnes G-function. In this talk I will describe a proof of the Conifold Gap Conjecture for the local projective plane, whereby the higher genus conifold Gromov-Witten generating series of local P2 are related to the thermodynamics of a certain statistical mechanical ensemble of repulsive particles on the positive half-line. As a corollary, this establishes the all-genus mirror principle for local P2 through the direct integration of the BCOV holomorphic anomaly equations.
On the conifold gap for local P2read_more
HG G 43
1 May 2026
16:00-17:30 		Prof. Dr. Jérémy Guéré
Université Grenoble Alpes
Details

Algebraic Geometry and Moduli Seminar

Title On the irrationality of cubic fourfolds
Speaker, Affiliation Prof. Dr. Jérémy Guéré, Université Grenoble Alpes
Date, Time 1 May 2026, 16:00-17:30
Location HG G 43
Abstract First, I will review the construction of atoms, beginning with an overview at the formal level before addressing the technical difficulties that necessitate the use of non-Archimedean fields. I will also discuss the behavior of the Hodge structure under Iritani's blow-up formula. Then, I will introduce a new atomic invariant and provide the proof for the following theorem: if a smooth complex cubic fourfold is rational, then its primitive cohomology is isomorphic, as a rational Hodge structure, to the shifted middle cohomology of a projective K3 surface. The proof relies on explicit computations for surfaces that I will present.
On the irrationality of cubic fourfoldsread_more
HG G 43
10 June 2026
13:30-15:00 		Prof. Dr. Hannah Larson
UC Berkely
Details

Algebraic Geometry and Moduli Seminar

Title Tautological classes on the strata of differentials
Speaker, Affiliation Prof. Dr. Hannah Larson, UC Berkely
Date, Time 10 June 2026, 13:30-15:00
Location HG G 43
Tautological classes on the strata of differentials
HG G 43
3 July 2026
13:30-15:00 		Prof. Dr. Longting Wu
SUSTECH
Details

Algebraic Geometry and Moduli Seminar

Title Virasoro constraints for orbifold curves
Speaker, Affiliation Prof. Dr. Longting Wu, SUSTECH
Date, Time 3 July 2026, 13:30-15:00
Location HG G 43
Abstract I will first review the Virasoro constraints for Gromov–Witten theory and the curve case proved by Okounkov and Pandharipande. I will then discuss ongoing work on extending these constraints to orbifold curves using degeneration techniques. 
Virasoro constraints for orbifold curvesread_more
HG G 43
17 July 2026
16:00-17:30 		Dr. Sam Canning
ETH Zürich
Details

Algebraic Geometry and Moduli Seminar

Title Moduli of lattice polarized K3 surfaces
Speaker, Affiliation Dr. Sam Canning, ETH Zürich
Date, Time 17 July 2026, 16:00-17:30
Location HG G 43
Abstract The definition of lattice polarized K3 surfaces has recently changed. I will attempt to explain the modified theory by Alexeev and Engel and its consequences with a particular focus on the intersection theory of Noether-Lefschetz cycles.
Moduli of lattice polarized K3 surfacesread_more
HG G 43
22 July 2026
13:30-15:00 		Aitor Iribar López
ETH Zürich
Details

Algebraic Geometry and Moduli Seminar

Title Simplified Kudla-Millson construction
Speaker, Affiliation Aitor Iribar López, ETH Zürich
Date, Time 22 July 2026, 13:30-15:00
Location HG G 43
Abstract In their celebrated work 30 years ago, Kudla and Millson constructed modular forms with values in the cohomology of locally symmetric spaces. For spaces that parametrize variations of Hodge structures of weight 2, a connection with work of Mathai and Quillen on superconnections was done by Garcia 10 years ago. A more careful examination of the work shows that the definition is in fact very simple. This simple formula allows us, in work with Garcia and Greer, to show modularity of Noether-Lefschetz cycles on $\mathcal A_g$. In the talk, I will review the main ideas behind the proof of modularity of special cycles using Mathai-Quillen forms with an emphasis on the case of K3 surfaces. This will serve as a preparation for the next talk, where the proof with Garcia and Greer will be discussed.
Simplified Kudla-Millson constructionread_more
HG G 43
23 July 2026
13:30-15:00 		Prof. Dr. Emanuel Scheidegger
Peking University
Details

Algebraic Geometry and Moduli Seminar

Title Enumerative invariants for orbifold Calabi-Yau threefolds
Speaker, Affiliation Prof. Dr. Emanuel Scheidegger, Peking University
Date, Time 23 July 2026, 13:30-15:00
Location HG G 43
Abstract We study orbifold Calabi-Yau hypersurfaces in weighted projective stacks from the point of view of the gauged linear sigma model. We give a very brief introduction to the gauged linear sigma model which is a physics version of quasimap theory and review some general conjectures. We explain how these conjectures allow for determination of the orbifold Gromov-Witten invariants without using Gromov-Witten or quasimap theory.
Enumerative invariants for orbifold Calabi-Yau threefoldsread_more
HG G 43
24 July 2026
16:00-17:30 		Aitor Iribar López
ETH Zürich
Details

Algebraic Geometry and Moduli Seminar

Title Kudla-Millson theory on A_g
Speaker, Affiliation Aitor Iribar López, ETH Zürich
Date, Time 24 July 2026, 16:00-17:30
Location HG G 43
Abstract The expectation, which was conjectured by Kudla and proven in several instances by several mathematicians, is that the Kudla-Millson forms extend to the toroidal compactifications of Shimura varieties and still preserve modularity in a certain way. In joint work with Garcia and Greer, we confirm this expectation on the compactification of $\mathcal A_1 \times \mathcal A_{g}$ obtained by adding the cusp and use it to show modularity of Noether-Lefschetz cycles. In the talk I will discuss approaches to Kudla's conjecture and give our proof of modularity. If time permits, I will talk about an extension to mixed Shimura varieties.
Kudla-Millson theory on A_gread_more
HG G 43
31 July 2026
16:00-17:30 		Prof. Dr. John Alexander Cruz Morales
National University of Colombia
Details

Algebraic Geometry and Moduli Seminar

Title Mixed Tate motives and mirror symmetry for Calabi-Yau threefolds
Speaker, Affiliation Prof. Dr. John Alexander Cruz Morales, National University of Colombia
Date, Time 31 July 2026, 16:00-17:30
Location HG G 43
Abstract In their seminal paper, Candelas, de la Ossa, Green, and Parkes discovered the appearance of the number (\chi(X)\zeta(3)) in their study of mirror symmetry for the quintic threefold. This quantity was later understood as a manifestation of the Gamma class. More recently, Candelas, de la Ossa, and van Straten, in their study of local zeta functions in the context of mirror symmetry, found an analogous quantity, (\chi(X)\zeta_p(3)), involving the (p)-adic zeta value (\zeta_p(3)). In this talk, I will discuss the motivic origin of the appearance of both (\zeta(3)) and (\zeta_p(3)) in this setting. This is joint work in progress with Michael Harris, Minhyong Kim, and Wenzhe Yang.
Mixed Tate motives and mirror symmetry for Calabi-Yau threefoldsread_more
HG G 43

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