Emmy Noether Seminar

Seminar of the Emmy Noether Junior Research Group “Smoothings from log resolutions and applications” at the Institute of Algebraic Geometry, Leibniz University Hannover .

Upcoming Talks

19 October 2026
11:00-12:00, room g117
Zhuang He
University of Turin
Picard ranks of Gorenstein toric Fano varieties and convex geometry of reflexive polytopes
Abstract
Reflexive polytopes are lattice polytopes such that every facet is of lattice distance one from the origin. Introduced by Batyrev, reflexive polytopes are at a position connecting toric geometry, convex geometry and mirror symmetry. The toric varieties associated with reflexive polytopes are exactly those that are Gorenstein and Fano. Casagrande proved that in the Q-factorial case, the Picard ranks of the associated toric varieties are at most twice the dimension. In this talk, I will present a new upper bound of the sum of the Picard ranks of a polar pair of Gorenstein toric Fano varieties of dimension d>=3, by the number of facets of the reflexive polytopes minus (d - 1). This generalizes Eikelberg's theory of non-Q-factorial toric Picard groups. I will report some work in progress, including a description of those polar pairs with relatively large Picard rank sums, and a conjectural structure on d-dimensional reflexive polytopes indexed by information on their Picard ranks.
16 November 2026
11:00-12:00, room g117
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14 December 2026
11:00-12:00, room g117
Milena Wrobel (tbc)
Otto von Guericke University Magdeburg
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11 January 2027
11:00-12:00, room g117
Bejamin Nill
Otto von Guericke University Magdeburg
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Past Talks

8 July 2026
14:30-15:30, room g117
Helge Ruddat
University of Stavanger
Clusters, Twistors and Stability Conditions
Abstract
We consider a mutation-finite quiver Q. Associated to Q are two interesting complex manifolds: (1) the space of stability conditions for the derived CY3 category of the Ginzburg algebra associated to the quiver, (2) the complex cluster Poisson variety. Each of these manifolds is constructed from the combinatorics of the quiver, though in very different ways. Tom Bridgeland and I introduce an "interpolation" of these complex manifolds: we give a construction of a complex manifold together with a submersion to the complex plane which we call the stability twistor space. The fiber over the origin is a finite quotient of the space of stability conditions whereas every other fiber is an etale cover of the cluster Poisson variety associated to the quiver. This etale map is a generalization of Thurston's grafting map. Constructing sections of the twistor family is closely related to solving the Riemann-Hilbert problem that encodes the Donaldson-Thomas invariants.
24 June 2026
14:30-15:30, room g117
Alejandro Ovalle
Leibniz University Hannover
Enumerative geometry of K3s: stable pairs and BPS invariants
Abstract
23 June 2026
16:30-17:30, room f128
Simon Felten
University of Oxford
Generically log smooth families via generators and relations
Abstract
A generically log smooth (gls) family is a degeneration f: X → 𝔸¹ of algebraic varieties which is log smooth in relative codimension one; as such, they are the logarithmic analog of families of normal varieties. Gls families play a fundamental role in smoothing reducible schemes because most of them do not admit a global log smooth structure. With a few exceptions, the log singularities of gls families are still poorly understood; it is therefore useful to study explicit examples. In this talk, I present the first general algorithmic tool to show that a family f: X → 𝔸¹ given by explicit generators and relations X = Spec 𝕜[t,x₁,...,xₙ]/(f₁,...,fᵣ) is indeed log smooth in relative codimension one, hence a gls family.
10 June 2026
14:30-15:30, room g117
Matej Filip
University of Ljubljana
Deformations of toric Gorenstein Fano varieties
Abstract

Given a Laurent polynomial with reflexive Newton polytope, we give a criterion ensuring that it gives rise to a deformation family with smooth general fibre. One-parameter deformations in this family correspond to mutations of the Laurent polynomial.

In dimension three, the smooth fibres arising from this construction include all 98 deformation families of very ample smooth Fano threefolds. This is an upcoming result that generalises the published work Laurent Polynomials and Deformations of Non-Isolated Gorenstein Toric Singularities.

Building on that framework, I will also outline evidence towards a conjecture of Corti–Filip–Petracci predicting a one-to-one correspondence between 0-mutable Laurent polynomials and the smoothing deformation components of three-dimensional affine Gorenstein toric varieties.