# Sommersemester 2017

Datum

Vortragender

Titel

13. April (12:00-13:00, a410)Matthias Nickel (Frankfurt)

Algebraic volumes of divisors (Abstract)

20. AprilFiruza Mamedova (Hannover)

Equivariant indices of 1-forms on varieties (Abstract)

27. AprilLucas Braune (Riemann-Fellow)

Irrational Complete Intersections (Abstract)

2. Mai (10:00 - 11:00, c311)Keiji Oguiso (Tokyo)

A few explicit examples of complex dynamics of inertia groups on surfaces - a question of Professor Igor Dolgachev (Abstract)

4. Mai (16:30 - 17:30)Ichiro Shimada (Hiroshima)On an Enriques surface associated with a quartic Hessian surface (Abstract)
11. MaiVíctor González Alonso (Hannover)Ranks of Kodaira-Spencer classes and Clifford indices. (Abstract)
18. MaiMagdaleen Marais (Riemann-Fellow, Pretoria)

Algorithmic Classification of Real (and Complex) Singularities (Abstract)

1. JuniJason Lo (Northridge)

Behaviour of slope stable sheaves under a Fourier-Mukai transform (Abstract)

22. JuniZiyu Zhang (Hannover)Singularities of moduli of sheaves on K3 surfaces and formality (Abstract)
29. JuniMatt Bainbridge (Indiana Univ.)Compactifications of strata of holomorphic one-forms (Abstract)
6. JuliGhislain Fourier (Hannover)Linear degenerations of flag varieties (Abstract)

13. Juli

Ben Moonen (Nijmegen)

Families of surfaces with many CM fibres (Abstract)

21. August* (14:15)

Toshiyuki Katsura (Hosei Univ., Tokyo)

Finite automorphism groups of Enriques surfaces in characteristic 2 (Abstract)

21. September* (14:15)Mauro Fortuna (Hannover)

Rationality of some cubic fourfolds with automorphisms (Abstract)

# Wintersemester 2016/17

Datum

Vortragender

Titel

20. Oktober

Carsten Liese (Hannover)

The KSBA compactification of the moduli space of degree 2 K3 pairs: a toroidal interpretation (Abstract)

27. Oktober

François Charles (Paris-Sud)

Arithmetic Bertini theorems (Abstract)

3. November

Gregor Bruns (Riemann)

Stability of normal bundles of canonical curves (Abstract)

9. November*

Sara Torelli (Pavia)

Massey products and Fujita decomposition (Abstract)

10. November*

Filippo Francesco Favale (Trento)

A twisted bicanonical system with base point (Abstract)

17. November

Stefan Schreieder (Bonn)

Generic vanishing and minimal cohomology classes on abelian fivefolds (Abstract)

24. November*David Ploog (FU Berlin)Negative divisors on surfaces (Abstract)

1. Dezember

Falko Gauß (Mannheim)

The moduli space of marked singularities (Abstract)

8. DezemberNorbert Hoffmann (Limerick/Riemann)

Universal torsors over degenerating del Pezzo surfaces (Abstract)

15. Dezember

Piotr Pokora (Hannover)

Curve arrangements and their H-indices (Abstract)

21. Dezember* (12:00-13:00)Luca Schaffler (Athens, Georgia)

The KSBA compactification of the moduli space of $D_{1,6}$-polarized Enriques surfaces (Abstract)

22. DezemberBernd Schober (Toronto)

Some difficulties in resolution of singularities in positive characteristic (Abstract)

11. Januar*(15:30-16:00)

Patrick Bloß (Frankfurt)

Die Deligne-Mumford-Kompaktizierung von
Hilbert-Moduldreifaltigkeiten als toroidale
Kompaktizierung (Abstract)

12. Januar

Juan J. Nuño Ballesteros (Valencia)

A Jacobian module for disentanglements and applications to Mond's conjecture (Abstract)

13. Januar (10:00 - 10:40, f303)

Andrea T. Ricolfi

(Stavanger)

Curve counting via the Quot scheme (Abstract)

25. Januar (14:00-15:00, g123)César Martínez (Caen)An arithmetic Bernstein-Kusnirenko inequality (Abstract)
26. JanuarSara Perna (Riemann)Siegel Modular Forms: Some Geometric Applications (Abstract)
2. FebruarAnn-Kathrin Stegmann (Hannover)

GIT Moduli Spaces of Certain Singular Cubic Fourfolds (Abstract)

9. Februar* (11:00)

Dirk Siersma (Utrecht)

Milnor fibre homology via deformation for non-isolated singularities (Abstract)

20. Februar (14:00- 15:00)

Daniele Agostini (HU Berlin)

Equations and syzygies of (abelian) surfaces (Abstract)

# Sommersemester 2016

Datum

Vortragender

Titel

7. April Firuza Mamedova (Moscow State / LUH)

Algebraic formulae for equivariant indices of vector fields on singular varieties (Abstract)

14. AprilSamuel Grushevsky (Stony Brook)Intersection cohomology of the moduli of abelian varieties and compactifications (Abstract)
21. AprilFabian Reede

Line bundles on noncommutative algebraic varieties (Abstract)

27. April (14:15-15:15, g117)Janko Böhm (Kaiserslautern)

Modular Techniques in Computational Algebraic Geometry (Abstract)

28. AprilAndreas HocheneggerSpherelike divisors (Abstract)
2. Mai (10:30-11:30, g117)Andrea CattaneoBeauville-type involutions on the Hilbert scheme of two points on a K3 surface (Abstract)
2. Mai (14:15-15-15, f428)Toshiyuki Katsura (Hosei)

Zariski K3 surfaces (Abstract)

12. MaiLuca Tasin

On a classical problem about Chern numbers (Abstract)

19. Mai (16-17, g117)

Matthias ZachThe Topology of Matrix Singularities (Abstract)
26. MaiEnrico Fatighenti (Warwick)Hodge Theory, deformations of affine cones and beyond (Abstract)
2. Juni (g117)

Zhiyuan Li (Bonn)

Cycle classes on moduli space of K3 surfaces (Abstract)
9. Juni (g117)Sebastian Casalaina-Martin (Boulder, Colorado)

Descending cohomolgy geometrically (Abstract)

16. JuniElisabeth Werner (Hannover)

Orbifold Jacobian Algebras and Orbifold Euler Characteristics (Abstract)

30. JuniNathan Priddis (Hannover)

A Landau--Ginzburg model of Borcea--Voisin mirror symmetry (Abstract)

7. Juli (g117)

Yuecheng Zhu (Pennsylvania)

modular compactification of moduli of polarized abelian varieties (Abstract)

12. Juli (10:15-11:15, f442)Alessandra Sarti (Poitiers)

Explicit Schoen surfaces (Abstract)

12. September (14:15-15:15, f309)Federico Lo Bianco (Rennes)

On the primitivity of birational transformations of irreducible holomorphic symplectic manifolds (Abstract)

# Wintersemester 2015/16

Datum

Vortragender

Titel

7. Oktober (14:15-15:15, g117)Elena Martinengo

Singularities of moduli spaces of sheaves on K3 surfaces (Abstract)

15. Oktober Ana Ros Camacho

Strangely dual orbifold equivalence (Abstract)

22. OktoberFrederik Tietz Ferns and other plants (Abstract)
29. OktoberCharles Vial (Cambridge)

On multiplicative weight decompositions (Abstract)

5. November (*)David Ploog

Semistability of Picard sheaves and a generalised Clifford theorem

(Abstract)
12. November Víctor González AlonsoWhich ideals are multiplier ideals? (Abstract)
26. NovemberMihai Tibar (Lille)

Vanishing homology of singular projective hypersurfaces (Abstract)

3. Dezember (*)Piotr Pikora (Mainz / Krakau)On the bounded negativity conjecture (Abstract)
10. DezemberQuentin GendronÜber den Abschluss der Strata Abelscher
Differentiale (Abstract)
16. Dezemeber (12-13, f309)Benjamin Schmidt (Ohio State)Stability Conditions on Threefolds - Some Wall-Crossings (Abstract)
17. DezemeberPatrick Graf (Bayreuth)Algebraic approximation of Kähler threefolds with Kodaira dimension zero (Abstract)
7. JanuarNiels Lindner

Density of hypersurfaces with defect (Abstract)

14. JanuarMartin Möller (Frankfurt)

Quasimodulformen und Asymptotik von Hurwitzzahlen zu Torusüberlagerungen (Abstract)

21. JanuarBernd Schober

A polyhedral characterization of quasi-ordinary singularities (Abstract)

26. Januar (12-13, f442)Atsushi Takahashi (Osaka)

On entropies of autoequivalences on smooth projective varieties (Abstract)

3. Februar (12-13, f309)Cecília Salgado (Rio)

Classification of elliptic fibrations on certain K3 surfaces (Abstract)

16. Februar (15:30-16:30, f309)Vincent Cossart (Versailles)

Resolution of Singularities, characteristic $p>0$ or mixed characteristic (Abstract)

18. FebruarAnnabelle Hartmann (Bonn)Equivariant motivic integration and the quotient map on the equivariant Grothendieck ring (Abstract)
23. Februar (11:15-12:15, f309)Roberto LafaceThe field of moduli of singular K3 surfaces (Abstract)
3. März (14:15-15:15, g117)Stephen Coughlan

Calabi-Yau threefolds in codimension 4 (Abstract)

10. März (16:30-17:30, f309)Stefan Kebekus (Freiburg)Higgs sheaves on singular spaces and the Miyaoka-Yau Inequality for minimal varieties of general type (Abstract)

Datum

Vortragender

Titel

16. AprilBernd SchoberResolution of Singularities In Dimension Two (Abstract)

23. April*

Davide Veniani

Counting lines on quartics: new techniques and results (Abstract)

30. AprilElisa Postinghel

Positivity of line bundles on blown-up projective spaces (Abstract)

7. MaiMichal KapustkaEPW cubes (Abstract)
21. MaiWenhao Ou (Grenoble)Lagrangian fibrations on symplectic fourfolds (Abstract)
2. Juni

Benjamin Bakker (HU Berlin)

The Kodaira dimension of complex hyperbolic manifolds with cusps (Abstract)
18. JuniSimon Brandhorst

Dynamics on a supersingular K3 surface and automorphisms of Salem degree 22 (Abstract)

30. Juni (14:15-15:15, a410)Sabir Gusein-Zade (Moscow State)Higher order generalized Euler characteristics and generating series (Abstract)
9. Juli

Yonatan Harpaz (École Normale Supérieure):

The Hasse principle for generalized Kummer varieties (Abstract)

16. JuliNathan PriddisMirror Symmetry for K3 surfaces (Abstract)
16. JuliJürgen Hausen (Tübingen)Fano varieties with torus action (Abstract)
6. August (14-15, F309)Lars Halle (Kopenhagen)

Equivariant potential good reduction, and motivic zeta functions (Abstract)

7. September (13:30-14:30)Hisanori Ohashi (Tokyo University of Science)Non-semi-symplectic automorphisms of Enriques surfaces (Abstract)
8. September (13:30-14:30)Taro Sano (Kyoto)

Deformations of cones over K3 surfaces (Abstract)

10. September (13:30-14:30)Kentaro Mitsui (Bordeaux / Kobe)Closed points on torsors under abelian varieties (Abstract)
14. September (14:15-15:15)Samuel Grushevsky (Stony Brook)Shimura curves in the Torelli locus in low genus (Abstract)
22. September (14:15-15:15, g117)Tetsuji Shioda (Rikkyo)

The MWL-algorithm for constructing cubic surfaces (Abstract)

24. September (14:15-15:15, g117)Maxim Smirnov

On quantum cohomology of isotropic Grassmannians (Abstract)

30. September (14:15-15:15, g117)Xuntao Hu (Stony Brook) Modular Form for Hyperflex Locus in M_3 (Abstract)
1. Oktober (14:15-15:15, g117)Elena Martinengo

Singularities of moduli spaces of sheaves on K3 surfaces (Abstract)

15. Oktober Ana Ros Camacho

Strangely dual orbifold equivalence (Abstract)

# Wintersemester 2014/15

Datum

Vortragender

Titel

9. Oktober

Stephen Coughlan

Elliptic Gorenstein 3-fold singularities and canonical threefolds (Abstract)

16. Oktober

Johannes Rauh

Algebraic Statistics and Conditional Independence (Abstract)

20. Oktober (13:00-14:00, a410)

Gavin Brown

Calabi-Yau 3-folds via Tom and Jerry (Abstract)

23. Oktober

Víctor González Alonso

Effective computation of multiplier ideals on rational surface singularities (Abstract)

30. Oktober

Tomasz Szemberg (Krakau, Polen)

Bounded negativity and arrangements of lines (Abstract)

31. Oktober (11:00-12:00, g117)

Sönke Rollenske (Bielefeld)

Stable surfaces: examples, results and open questions (Abstract)

6. November

Partially ample line bundles on toric varieties (Abstract)

13. November

Elena Martinengo

Mori dream stacks (Abstract)

17. Novemer

Miguel Marco

Numerical conditions of Max Noether's theorem (Abstract)

20. November (16:00-17:00)

Sławek Rams

On Enriques surfaces with four cusps (Abstract)

27. November

Alexey Basalaev

Mirror symmetry for simple elliptic singularity with a group action (Abstract)

3. Dezember         (16-17, a410)

Martin Bright (Leiden)

The Brauer-Manin obstruction and reduction mod p (Abstract)

4. Dezember

Olivia Dumitrescu

Elementary (-1) cycles in P^n (Abstract)

9. Dezember

Henning Krause

11. Dezember

Christian Lehn

Rational curves on singular cubic fourfolds (Abstract)

16. Dezember (10-11, f428)

Alessandra Sarti

Pell's equation and automorphisms of Hilb^2(K3) (Abstract)

18. Dezember (15-16, f442)

Milena Hering

Projective normality of tropical curves (Abstract)

18. Dezember (17-18, f442)

Arend Bayer (Edinburgh)

The space of stability conditions on abelian threefolds (and on some Calabi-Yau threefolds) (Abstract)

8. Januar

Tong Zhang (Alberta)

Relative Noether inequality and geography of irregular varieties (Abstract)

12. Januar       (16-17, a410)

Norbert Hoffmann (Mary Immaculate College, Limerick)

Essential Dimension of Vector Bundles (Abstract)

15. Januar

André Kappes (Frankfurt)

Kontsevich's formula for the sum of Lyapunov exponents (Abstract)

22. Januar

Marcello Bernardara (Toulouse)

Homological projective duality for determinantal varieties (Abstract)

29. Januar        (a410)

Frederik Tietz

Homological stability for Hurwitz spaces of S_3-covers (Abstract)

5. Februar (10-12, f309)

Roberto Laface

Fields of deﬁnition of singular K3 surfaces and classiﬁcation of their Q-models (Abstract)

18. Februar (10-11, g117)

Alexander Molnar (Queen's University)

Arithmetic and intermediate Jacobians of some rigid Calabi-Yau threefolds (Abstract)

19. Februar (15-16:30, g117)

Matthias Zach

Computation of Vanishing Cycles via blowup of Syzygies (Abstract)

5. März (11:15-12:15, g117)

Toshiyuki Katsura (Tokyo)

Configurations of smooth rational curves on superspecial K3 surfaces in small characteristics (Abstract)

11. März (14:30-15:30, b305)Janos Kollar (IAS)

The dual complex of Calabi--Yau pairs (Abstract)

12. März (11:15-12:15, f309)Andreas Hochenegger

Maps between Mori Dream spaces (Abstract)

17. März (11:15-12:15, f309)Ronan Terpereau (Mainz)Moduli spaces of (G,h)-constellations (Abstract)
23. März (15:15-16:45, g117)Thomas Peternell (Bayreuth)

The nef cone of a Calabi-Yau threefold (Abstract)

# Sommersemester 2014

Datum

Vortragender

Titel

27. März (14-16)

Gilberto Bini (Milano, IT)

Not Only Calabi-Yau Threefolds (Abstract)

10. April

Atsushi Takahashi (Osaka, JP)

Orbifold Projective Lines and Extended Cuspidal Weyl Groups (Abstract)

17. April

Chiara Camere

Non-symplectic automorphisms of holomorphic symplectic manifolds of K3^[2]-type (Abstract)

24. April

Wenfei Liu

Towards Albanese maps of stable surfaces (Abstract)

28. April (12-13:30, f102)

On the automorphism groups of certain singular K3 surfaces (Abstract)

8. Mai (*)

Nero Budur (Leuven)

Cohomology jump loci (Abstract)

22. Mai

Paola Comparin (Poitiers)

Van Geemen-Sarti involutions and elliptic fibrations on K3 surfaces (Abstract)

2. Juni (14-15:30, a410)

Davide Veniani

Lines on mildly singular quartics (Abstract)

3. Juni (14-15:30, f442)

Ana-Maria Castravet (Ohio State)

Birational geometry of moduli spaces of stable rational curves (Abstract)

10. Juni (14-16, *)

Jesse Leo Kass (South Carolina)

How to deform a n-by-(n+1) matrix (Abstract)

12. Juni (14-16, *)

Matteo Penegini (Milano / Riemann)

Irrational pencils on surfaces with $p_g=q=2$ (Abstract)

19. Juni

Malte Wandel (RIMS)

Induced automorphisms on manifolds of K3^[n]-type (Abstract)

26. Juni (11-12, a310)

Die Vermutung von Kudla und formale Fourier-Jacobi-Reihen (Abstract)

30. Juni (14-15:30, a410)

Kubische Flächen - Modulräume und Arithmetik (Abstract)

3. Juli*

Elisabeth Werner

Frobenius structures for cusp polynomials with group actions (Abstract)

7. Juli (12-14, f102)

Balazs Szendroi (Oxford)

Euler characteristics of Hilbert schemes of points of ADE surfaces (Abstract)

10. Juli*

Christian Lehn (Jussieu)

Log-minimal models for symplectic varieties (Abstract)

17. Juli (15:15-16:45)

Stefan Müller-Stach (Mainz)

What is a period? (Abstract)

24. Juli

Nathan Priddis

Landau-Ginzburg/Calabi-Yau correspondence for Fermat hypersurfaces (Abstract)

WiSe 2013/14

Datum

Vortragender

Titel

10. Oktober (10:00-12:00)

Roberto Laface

On Zariski Decomposition With and Without Support

Abstract
Zariski Decomposition was firstly introduced by O. Zariski in 1962. In its original version, it allows to write any effective divisor D on a projective surface as the sum D=P+N of a nef divisor P, and an effective divisor N whose intersection matrix defines a negative definite quadratic form (they are respectively called positive and negative part of D). Later in 1979, the result was improved by T. Fujita, who extended it to pseudo-effective divisors. In 2008, Y. Miyaoka introduced the Zariski Decomposition for effective divisors with support in a negative definite cycle, which he needed in his study of the surfaces of general type: this version allows us to choose the negative part N.

The lecture aims at connecting the works of the authors presented in this timeline. After recalling the statements of Zariski and Fujita, we discuss the Zariski Decomposition with support, of which we give a different proof (following an idea of T. Bauer). Afterwards, we generalize Miyaoka's result in two ways: on one hand, we extend the result to any divisor D (so it does not have to be effective); on the other, we prove the result for pseudo-effective divisors with the relaxed hypothesis that the support is in any cycle, not necessarily negative definite. Finally, it comes naturally that the Zariski Decomposition for pseudo-effective divisors introduced by Fujita can be realized by iterating the Zariski Decomposition with support.

N.B.: The talk will be based on the following article:

http://arxiv.org/abs/1306.4697

17. Oktober

Alexey Basalev

3-dimensional Frobenius manifolds via elliptic curves

Abstract We investigate 3-dimensional Frobenius manifolds that appear as the subvarieties in the deformation space of simple elliptic singularities. We set up the connection between such Frobenius manifolds and elliptic curves. With the help of elliptic curves theory we give the classification of such Frobenius manifolds having additional symmetries and defined over Q.

24. Oktober

Slawek Rams

On quartic surfaces with many lines.

Abstract We show that a smooth quartic surface over algebraically closed field of characteristic different from 2,3 contains at most 64 lines. We discuss properties of quartics with lines of the second kind (joint work with Prof. M. Schuett (LU Hannover).

31. Oktover

Olivia Dumitrescu

Interpolation problems in P^n

Abstract We give an overview of interpolation problems in P^n. We investigate the speciality of effective linear systems in P^n with assigned multiple points and linear base locus. For this, we compute the cohomology groups of the strict transforms of divisors via the blow-up of their linear base locus. (with C. Brambilla and E. Postinghel) We extend this computations to non-effective divisors in P^n. In particular this shows that linear cycles are special effect varieties for effective linear systems interpolating points. Using the birational geometry of Cremona transformantion we give new classes of special effect varieties of dimension 1 and 2 in P^4. (with R. Miranda) This generalizes the elemetary (-1) curves of Laface-Ugalia in P^3, and it also give information on the Effective cone of the Blown up P^4 in arbitrary number of points.

14. November (16:00-17:00)

Elisabeth Werner

Algebraic geometric Codes and Lattices

Abstract We will give a short overwiew of codes and lattices and their connections. Then we want to construct codes and lattices from function fields of algebraic curves over finite fields. We fix a finite set of points. The code constructions are on the one hand evaluations of a linear system related to a divisor and on the other hand residues of linear systems of differentials. The lattice construction is related to lattices of units from number fields and makes use of principal divisors. In the end we will find a connection between this algebraic-geometric codes and lattices.

21. November

Discrete derived categories

Abstract Discrete derived categories, as defined by Vossieck, form a class of triangulated categories which are sufficiently simple to make explicit computation possible, but also non-trivial enough to manifest interesting behaviour. In this seminar, I will explain what they are, and talk about some recent work with D. Pauksztello and D. Ploog, where we study the autoequivalences and bounded t-structures on these categories. I will go on to describe work in progress, aiming to understand the corresponding spaces of Bridgeland stability conditions.

28. November

Christian Böhning (Hamburg)

Rationality problems: a bird's eye view

Abstract After a general introduction to and sample of guiding open
problems in the birational geometry of varieties close to the
rational ones, we discuss
(1) recent results for linear group quotients;
(2) the derived category and Hodge-theoretic approaches to
the irrationality problem for very general cubic fourfolds; their
shortcomings and ramifi cations (phantom categories); and
possible alternatives (dynamical spectra).

5. Dezember

Miguel Angel Marco Buzunariz

Euler characteristic, counting polynomial and Chern-Schwarz-MacPherson class of an algebraic set

Abstract Deducing the topology of an algebraic set from its defining equations is, in general, a difficult task. In this talk, a method to compute the Euler characteristic will be presented. Using the same method it is possible to compute a stronger invariant, that is directly related to the Chern-Schwarz-MacPherson class. We will also show how this stronger invariant is related to the problem of counting points of varieties over finite fields.

12. Dezember

Daniel Greb (Bochum)

Construction and variation of moduli spaces of sheaves on higher-dimensional base manifolds

Abstract While the variation of moduli spaces of H-slope/Gieseker-semistable sheaves on surfaces under change of the ample polarisation H is well-understood, research on the corresponding question in the case of higher-dimensional base manifolds revealed a number of pathologies. After presenting these, I will discuss recent joint work with Matei Toma (Nancy) and Julius Ross (Cambridge) which resolves some of these pathologies by looking at curves instead of divisors, and by embedding the moduli problem for sheaves into a moduli problem for quiver representations.

18. Dezember (10:00-12:00, g005)

Atsushi Takahashi

Weyl Groups and Artin Groups Associated to Orbifold Projective Lines

Abstract After explaining our motivation coming from mirror symmetry, we report on our recent study of a correspondence among orbifold projective lines, cusp singularities and cuspidal root systems. A conjectual relation among Weyl groups, Artin groups and the spaces of Bridgeland's stability conditions for some triangulated categories for orbifold projective lines will also be explained.

19. Dezember

Frederik Tietz

On homological stability of certain moduli spaces

Abstract (Co-)Homological stability phenomena for sequences of spaces or groups arise in many classical and modern contexts. In this talk, a few stability results are covered, including braid groups (Arnold), moduli of curves/mapping class groups (Harer, Madsen-Weiss), and Hurwitz spaces (Ellenberg-Venkatesh-Westerland). Emphasis lies on the presentation of the algebro-geometric and topological ideas that lie behind the theorems and their proofs. We will show how these results could fit into a common framework in order to obtain further stability results.

9. Januar

Matthias Zach

On the topology of simple isolated Cohen-Macaulay codimension 2 singularities in IC^5

Abstract The simple isolated Cohen-Macaulay codimension 2 singularities were classified by Anne Fruehbis-Krueger and Alexander Neumer. They have a smooth base in their semi-universal deformation and hence a unique Milnor fiber. Contrary to the case of hypersurface singularities, for Cohen-Macaulay codimension 2 singularities in IC^5 there can be two nonvanishing betti numbers contributing to the defect of the euler characteristic in a smoothing. Recently James Damon and Brian Pike did computations of the latter for some classified members revealing some peculiarities. I will present explicit computations of the vanishing cycles and their interplay for certain families and hope to discuss possible conjectures for the general behaviour.

16. Januar

Gunther Cornelissen (Utrecht)

Gonality of curves and graphs

Abstract The gonality of a smooth projective curve X over a field k is defined as the minimal degree of a non-constant morphism from X to the projective line. If k is the complex numbers, X can be considered as a compact Riemann surface, and Li and Yau have established a lower bound on the gonality of X in terms of the hyperbolic volume and the first eigenvalue of the Laplacian of X. Such a bound has numerous applications, for example, it leads to a lower bound on the gonality of modular curves for congruence groups that is linear in the index of the group in the full modular group (Abramovich) and to bounds on rational points in families of field extensions (Frey et. al.) I will present a non-archimedean analogue of these facts. The first result is a comparison theorem between gonality of a curve and the so-called stable gonality of its reduction graphs (a new concept). The main result is a lower bound for stable graph gonality in terms of the first eigenvalue of the Laplacian and some “volume” of the original graph (this can be seen as a substitute for graphs of the Li–Yau inequality from differential geometry, although the strict analogue of the original inequality fails for general graphs). We apply the results to give a lower bound for the gonality of arbitrary Drinfeld modular curves over finite fields and for general congruence subgroups Γ of analogous to the result of Abramovich. Another application is to rational points, and to lower bounds on the modular degree of certain elliptic curves over function fields (solving a problem of Papikian).

(joint work with Janne Kool and Fumiharu Kato)

20. Januar (11:00-12:00, f442)

Benjamin Bakker

The geometric Frey-Mazur conjecture

Abstract A crucial step in the proof of Fermat's last theorem was Frey's insight that a nontrivial solution would yield an elliptic curve with modular p-torsion but which was itself not modular. The connection between an elliptic curve and its p-torsion is very deep: a conjecture of Frey and Mazur, stating that the p-torsion group scheme actually determines the elliptic curve up to isogeny (at least when p>13), implies an asymptotic generalization of Fermat's last theorem. We study geometric analogs of this conjecture, and show that over function fields the map from isogeny classes of elliptic curves to their p-torsion group scheme is one-to-one. Our proof involves understanding curves on certain Shimura varieties, and fundamentally uses the interaction between its hyperbolic and algebraic properties. This is joint work with Jacob Tsimerman.

23. Januar

Malek Joumaah

Moduli spaces of K3^[2]-type fourfolds with non-symplectic involutions

Abstract For a K3 surface S and a non-symplectic involution i on S, Nikulin has shown that the deformation type of (S,i) is determined by the invariant sublattice of H^2(S,Z). The corresponding moduli space is an arithmetic quotient of a bounded symmetric domain, and in particular a quasi-projective variety. We will see that the latter statement can be generalized to K3^[2]-type fourfolds in a slightly weaker form. However, for a given invariant sublattice, there can be several deformation classes, and we will discuss a way to describe them.

30. Januar

Benjamin Wieneck

Discriminant loci of Lagrangian fibrations

Abstract Lagrangian fibrations on irreducible holomorphic symplectic manifolds are higher dimensional generalizations of elliptic K3 surfaces. The discrimiant locus of such a fibration i.e. the set which parametrizes the singular fibers is projective of codimension 1. A natural question is if there is a more natural scheme structure on the discriminant locus than the trivial reduced one. Such a structure could lead to a classification. I will discuss some concepts with a view to fibrations on K3^[n] which are induced by elliptic K3 surfaces.

4. Februar (14:15-15:45)

Thomas Dedieu

Limits of pluri--tangent planes to K3 surfaces

Abstract I will discuss the following general question : given a family $X \to D$ of complex surfaces in $\mathbf{P} ^N$ with smooth general member (here $D$ stands for the complex unit disk), what are the limits as $t \in D$ tends to $0$ of the families of hyperplanes tangent in $d$ points to $X _t$, $t \neq 0$ ? (here $d$ is a given integer, smaller than $N$) I will give a complete answer in the two cases of smooth quartic hypersufaces in $\mathbf{P} ^3$ degenerating to (i) the union of four planes, and (ii) a Kummer surface. This will then be applied to the study of the irreducibility and enumerative geometry of the Severi varieties of quartic $K3$ surfaces. Eventually, I will sketch a conjectural to the question in general. This is joint work with Ciro Ciliberto.

25. Februar (10-12)

Toshiyuki Katsura (Hosei, Tokyo)

Some invariants of algebraic varieties in positive characteristic

Abstract We discuss relations between certain invariants of varieties in positive characteristic, like the $a$-number and the height of the Artin-Mazur formal group. We calculate the $a$-number for Fermat surfaces. (joint-work with G. van der Geer)

27. Februar (14:15-15:45*)

Mathieu Dutour

Lattices and perfect forms

Abstract Lattices are discrete subgroups of R^n and they have interest in geometry of numbers, algebra (root lattices), number theory (mass formulas), and algebraic geometry. I will explain the basics of lattice theory, the classical examples and how to compute with them. Then I will explain the perfect form theory, which is the simplest example of a reduction theory and gives a tessellation of the space of positive definite quadratic forms. Finally, if time allows, I will try to give some other reduction theories (i.e. tessellation of the space of quadratic forms): The L-type reduction theory and the central cone compactification. Within the limits of my knowledge, I will present the relation between such tessellations and the corresponding toroidal compactification of the moduli space Ag of principally polarized abelian varieties. Again if time allows, I will present the possible applications of the tesselations to cohomology computations. (slides)

SoSe 2013

Date

Speaker

Title

April 4 *

Klaus Hulek

On stable cohomology of compactifications of A_g

Abstract In this talk we shall discuss the stable cohomology of A_g and its compactifications. It is a classical result of Borel that A_g has stable cohomology. This was extended to the Satake compactification by Lee and Charney. We shall show that one cannot expect stable cohomology for the second Voronoi compactification. On the other hand we shall prove that the perfect cone compactification has stable cohomology. This is joint work with Sam Grushevsky and Orsola Tommasi.

April 11

Michael Lönne

The orbifold fundamental group of moduli spaces of elliptic surfaces

Abstract Over the complex numbers we consider different kinds of moduli problems for elliptic surfaces and the associated moduli spaces. Then we show how to solve the problem to get a finite presentation of their orbifold fundamental groups, where braid monodromy is the principal tool. This will be illustrated in the toy case of elliptic curves. If time permits we discuss possible relations symmetric domains.

April 18 *

Giovanni Mongardi (Roma/Bonn)

On natural deformations of symplectic automorphisms on manifolds of K3^[n] type

Abstract Given an automorphism group of a manifold of K3^[n] type it is natural to ask whether it can be obtained as deformations of automorphisms induced by some k3 surface. We prove that this is equivalent to a simple numerical condition.

April 22 * (16:15-17:45)

Slawek Cynk (Krakow)

One parameter families of Calabi-Yau 3-folds

Abstract One parameter families of Calabi-Yau manifolds are studied in the context of modularity, computation of Picard-Fuchs operator. There are two special classes of examples which are interesting and easy to study: desingularized fiber products and double octics. In the latter case Meyer classified examples defined over \mathbb Q. I will discuss certain examples, their properties and relations.

April 25

Gilberto Bini (Milano)

Some Remarks on Calabi-Yau Varieties

Abstract In this talk, we will describe some new Calabi-Yau threefolds which can be obtained as a quotient of a Calabi-Yau variety in a Fano fourfold. From these manifolds, we also get a surface of general type with q=p_g=0 a new fundamental group, and K^2=3. This is joint work with F. Favale, J. Neves and R. Pignatelli.

May 2

Michael Bogner (Mainz/Riemann)

Differential operators of Calabi-Yau type

Abstract Differential operators of Calabi-Yau type intend to describe periods of one-parameter families of Calabi-Yau manifolds which admit a point of maximally unipotent monodromy. In this talk, we discuss algebraic and arithmetic properties of these operators and present a method to classify and construct those whose local systems of solutions have low index of rigidity.

May 7

Bas Heijne

Computing the Picard number of Delsarte surfaces with only ADE-singularities.

Abstract In the eighties Shioda gave an algorithm to compute the Picard number of Delsarte surfaces. In this talke we will describe this algortihm. Then we will show how we can used this algorithm to give a closed formula for the Delsarte surfaces with only ADE-singularities.

May 30

Frithjof Schulze

The Inose model of singular K3 surfaces of class number 2

Abstract Singular K3 surfaces are connected to pairs of isogenous Elliptic curves with complex multiplication via a so called Shioda-Inose structure. This structure also gives rise to an elliptic fibration with a model that is always defined over a number field. In this talk I will explain the notion of the class number of singular K3 surface and explain why exactly half of the singular K3 surfaces with class number 2 are defined over the rational numbers. Along the way I will introduce the necessary concepts from classical number theory.

June 6

Nicola Tarasca

Counting Brill-Noether special points

Abstract We present a closed formula for the number of linear series with prescribed ramification at unassigned points on the general curve. The formula generalizes a result of Harris-Mumford for the case of pencils. We discuss several applications to divisor classes computations on moduli spaces of stable curves with marked points. This is joint work with Gavril Farkas.

June 13 *

Wim Veys (Leuven)

Generalized Monodromy Conjecture in dimension two

June 20 16:30 - 18:00

Aleksandr Pukhlikov (Liverpool)

Birationally rigid Fano varieties

Abstract In the talk, two recent results in the theory of birational rigidity of higher-dimensional Fano varieties will be discussed: the estimate for the codimension of the locus of non-rigid hypersurfaces of index one (joint result with Thomas Eckl) and birational superrigidity of complete intersections of quadrics and cubics.

June 20 18:30 - 20:00

Filippo Viviani (Roma)

Fourier-Mukai transform for compactified Jacobians

Abstract To every reduced (projective) curve X with planar singularities one can associate many fine compactified Jacobians, depending on the choice of a polarization on X, which are birational (possibly non-isomorphic) Calabi-Yau projective varieties with locally complete intersection singularities.
In a joint work with M. Melo and A. Rapagnetta, we define a Poincarè sheaf on the product of any two (possibly equal) fine compactified Jacobians of X and show that the integral transform with kernel the Poincar\'e sheaf is an equivalence of their derived categories, hence it defines a Fourier-Mukai transform.
This result can be interpreted in two ways.
First of all, when the two fine compactified Jacobians are equal, the above Fourier-Mukai transform provides a natural autoequivalence of the derived category of any fine compactified Jacobian of X, which generalizes the classical result of S. Mukai for Jacobians of smooth curves and the more recent result of D. Arinkin for compactified Jacobians of integral curves with planar singularities. This provides further evidence for the classical limit of the geometric Langlands conjecture (as formulated by R. Donagi and T. Pantev).
Second, when the two fine compactified Jacobians are different (and indeed possibly non-isomorphic), the above Fourier-Mukai transform provides a natural equivalence of their derived categories, thus it implies that any two fine compactified Jacobians of X are derived equivalent. This is in line with Kawamata's conjecture that birational Calabi-Yau (smooth) varieties should be derived equivalent and it seems to suggest an extension of this conjecture to (mildly) singular Calabi-Yau varieties.

June 27 *

Orsola Tommasi

Cohomology of moduli spaces of genus 2 curves and the Gorenstein conjecture

Abstract A main theme in the study of the cohomology of moduli spaces of curves is the study of the tautological ring, a subring generated by certain geometrically natural classes. One of the open questions is whether the tautological ring is a Gorenstein ring, as conjectured by Carel Faber in the case of smooth curves without marked points. In this talk we discuss an approach that allows to detect the existence of non-tautological classes in the cohomology ring of the moduli space of stable curves of genus 2 with sufficiently many marked points, such as those constructed by Graber and Pandharipande for \bar M_{2,20}. We use this to prove that the Gorenstein conjecture does not hold for these spaces.
This is joint work with Dan Petersen (KTH, Stockholm).

July 1 * 16:15-17:45

Barbara Fantechi (SISSA)

Moduli stacks of degenerations

Abstract A classical, ubiquitous idea in algebraic geometry is to use blowing up to resolve singularities. Artin stacks can be used to do this in families in a systematic way. We will give two basic examples: one is Jun Li's stack of expanded degenerations, the other is the stack used (implicitly) to define Fulton-MacPherson's space of configurations. We will start by outlining the necessary background on algebraic stacks, give a detailed construction of the first case and a sketch in the second, and explain how they show up in a number of moduli problems, where they allow to construct a compactification or improve an existing one. In particular we will cover the geometrical background of Jun Li's degeration formula for Gromov-Witten and other invariants.

July 3 16:15-17:45

Matteo Penegini

Surfaces isogenous to a product of curves, moduli spaces and finite groups

Abstract In this talk we shall present a group theoretical method to calculate the number of connected components of the moduli space of surfaces of general type isogenous to a product of curves. First we shall use this method in order to compute the number of connected component for irregular surfaces with ?=1. Later we shall present some results obtained together with S. Garion, where we give the asymptotic growth of the number of connected components of the moduli space of surfaces of general type corresponding to certain families of Beauville surfaces with group either PSL(2,p), or an alternating group, or a symmetric group or an abelian group. Finally we extend these results to regular surfaces isogenous to a product of curves.

July 4 *

Christian Lehn (Grenoble/Paris)

A new construction of symplectic manifolds of dimension 8

July 11

Justin Sawon (Chapel Hill)

Finiteness of Lagrangian fibrations

Abstract Irreducible holomorphic symplectic manifolds are one of the basic building blocks of manifolds with trivial canonical bundles. Surprising, the only fibrations they can admit are Lagrangian fibrations, with fibres that are Lagrangian with respect to the holomorphic symplectic structure. Ultimately, we would like to use Lagrangian fibrations to classify all holomorphic symplectic manifolds. In this talk I will describe why, after imposing some natural hypotheses, there are only finitely many deformation classes of Lagrangian fibrations. The talk will be based on the preprint arXiv:1212.6470.

July 16 * (15:00 - 16:30)

Maksym Fedorchuk (Boston)

GIT stability of Hilbert and Syzygy points of canonical curves

Abstract I will introduce the log minimal model program for the moduli space of Riemann surfaces M_g and explain how it gives rise to a sequence of modular compactifi cations of M_g. These include the Deligne-Mumford space of stable curves, but also much more recent compact moduli space of at worst tacnodal curves constructed by Hassett and Hyeon. I will then introduce a Geometric Invariant Theory problem concerning stability of the Hilbert points of (bi)canonical curve, sketch its solution in the generic case (joint with Alper and Smyth) and explain how it is extended to obtain GIT stability of the Syzygy points of canonical curves (current work-in-progress, joint with Deopurkar and Swinarski).

WiSe 2012/13

Datum

Vortragender

Titel

20. September

Slawomir Cynk (Krakow, POL)

Picard-Fuchs operator for double octic Calabi-Yau threefolds (Abstract)

4. Oktober*

Benjamin Wieneck

A family of Calabi-Yau threefolds without maximal unipotent monodromy (Abstract)

8. Oktober**

Jesse Kass

Two ways of degenerating the Jacobian are the same (Abstract)

18. Oktober

Slawomir Rams

On Calabi--Yau threefolds associated to a web of quadric

25. Oktober

Stefano Pascolutti

Modular Forms and the Looijenga Conjecture (Abstract)

1. November

Paola Frediani

On the Koszul cohomology of canonical and Prym-canonical binary curves (Abstract)

8. November

Matteo Tommasini

The Hodge-Deligne polynomials of some moduli spaces of coherent systems (Abstract)

15. November

Nicola Pagani

Moduli of abelian covers of elliptic curves (Abstract)

22. November

Pawel Sosna (Hamburg)

Construction of (quasi-)phantom categories on some surfaces of general type (Abstract)

29. November

Frederik Tietz (Göttingen)

Geometry of Projective Cycloids and Trochoids (Abstract)

10. December***

Vertical Brauer groups and del Pezzo surfaces of degree 4 (Abstract)

13. December

Chiara Camere

Lattice-polarized irreducible holomorphic symplectic manifolds (Abstract)

20. December

Anne Frühbis-Krüger

Algorithmic Resolution of Singularities: Hauser's Kangaroos in positive Characteristic (Abstract)

10. Januar

Malte Wandel

On non-symplectic involutions on manifolds of K3^[2]-type (Abstract)

17. Januar

Alex Degtyarev (Ankara)

On lines on smooth quartics (Abstract)

24. Januar

Alexey Basalaev

Frobenius manifolds in singularity theory: different approaches

31. Januar

Maxim Smirnov (MPI/IHES)

Towards quantum cohomology of $\overline{M}_{0,n}$  (Abstract)

7. Februar

Jakob Kröker

Algorithmic construction of Hurwitz maps (Abstract)

14. Februar****

Fabien Clery

Vector-valued Picard modular forms (Abstract)

18. Februar*****

Atsushi Takahashi (Osaka)

From Calabi-Yau dg categories to Frobenius manifolds via primitive forms: a work in progress (Abstract)

18. Februar******Matteo TommasiniOrbifolds as 2-categories  (Abstract)

19. Februar*******

Charles Siegel (IPMU)

The Schottky problem in genus 5
6. MärzJohannes Nicaise (Leuven)The Kontsevich-Soibelman skeleteon of a degeneration of Calabi-Yau varieties  (Abstract)

Anmerkungen:

* Der Termin findet von 14:15-15:15 Uhr in Raum g117 statt

** Der Termin findet von 15:15-16:45 Uhr in Raum g117 statt.

*** Der Termin findet von 14:15-15:45 Uhr in Raum c109 statt.

**** Der Termin findet von 15:00-16:30 Uhr in Raum g117 statt.

***** Der Termin findet von 10:15-11:45 Uhr in Raum g117 statt.

****** Der Termin findet von 14:15-15:45 Uhr in Raum f309 statt.

******* Der Termin findet von 14:15-15:45 Uhr in Raum g117 statt.

 SoSe 2012 Datum Vortragender Titel 12. April B. Szendrői (Oxford, GBR / FU Berlin) Nekrasov's formula and refined sheaf counting (Abstract) 19. April O. Tommasi Cohomology of local systems of low weight on M2 (Abstract) 26. April N. Broomhead Averaging t-structures (Abstract) 24. Mai A. Apostolov Correspondences between families of polarized irreducible symplectic manifolds (Abstract) 31. Mai V. Hoskins Finite and Infinite stratifications for sheaves (Abstract) 7. Juni F. Charles (Rennes, FRA) The Tate conjecture for holomorphic symplectic varieties (Abstract) 14. Juni M. Bolognesi (Rennes, FRA) Rational cubic fourfolds containing a plane with nontrivial Clifford invariant (Abstract) 21. Juni R. Vistorin Geometry of a special K3 surface (Abstract) 5. Juli F. Schulze Modularity and the construction of singular K3 surfaces (Abstract) 9. Juli* X. Bogomolec Lipman's Desingularization Algorithm (Abstract) 12. Juli M. Joumaah Automorphisms of certain deformations of the Hilbert scheme of two points on a K3 surface (Abstract) 19. Juli S. Rollenske (Bielefeld) Pluricanonical maps of stable surfaces (Abstract) August 28** Hisanori Ohashi (Nagoya University, Japan) On automorphisms of K3 surfaces and Enriques surfaces (Abstract) September 20*** Slawomir Cynk (Krakow) Picard-Fuchs operator for double octic Calabi-Yau threefolds (Abstract) Anmerkungen * Der Termin am Montag, 9.7.2012 findet von 10:15-11:45 Uhr in Raum g117 statt. ** Der Termin am Dienstag, 28/8/2012 findet von 15:15-16:45 Uhr in Raum a410. *** Der Termin am Donnerstag, 20/9/2012 findet von 14:15-15:45 Uhr in Raum a410.

 WiSe 2011/12 Datum Vortragender Titel 20. September* F. Kiraly (TU Berlin) Algebraische Geometrie im Machine Learning (Abstract) 4. Oktober** S. Cynk (Krakau, POL) Defect of a hypersurface via logarithmic differential forms (Abstract) 20. Oktober A. Basalaev Cohomological field theories on Losev-Manin mospace (Abstract) 27. Oktober C. Camere Involutions of holomorphic symplectic manifolds (Abstract) 3. November A. Krug (Augsburg) Extension groups of tautological sheaves on Hilbert schemes (Abstract) 24. November A. Hochenegger Exceptional Sequences on Toric Surfaces (Abstract) 1. Dezember T. Abdelgadir (MPI-Bonn) Quivers of sections on toric orbifolds (Abstract) 8. Dezember D.-Q. Zhang (Singapore) Automorphisms of positive entropy on compact Kahler manifolds (Abstract) 15. Dezember M. Miesener On the action of the automorphisms of the affine plane on semistable bundles (Abstract) 5. Januar D. Ploog K3 surfaces: quadratic forms and Fourier-Mukai partners (Abstract) 12. Januar M. Wandel K3 surfaces: quadratic forms and Fourier-Mukai partners (Abstract) 19. Januar J. Rüth Models of curves over local fields: normalization and valuations (Abstract) 26. Januar Y. Tschinkel (New York, USA) Rational points on algebraic varieties over function fields (Abstract) 2. Februar M. Kapranov (Yale, USA) Arithmetic Hall algebras (Abstract) 7. Februar*** A. Cattaneo (Milano, ITA) A journey through Elliptic CY threefolds (Abstract) Anmerkungen * Der Termin am Dienstag, 20.9.2011 findet von 14:00-15:30 Uhr in Raum g123 statt. ** Der Termin am Dienstag, 4.10.2011 findet von 16:15-17:45 Uhr in Raum g117 statt. *** Der Termin am Dienstag, 7.2.2012 findet von 14:15-15:45 Uhr in Raum g117 statt.

 SoSe 2011 Datum Vortragender Titel 24. März A. D. King (Bath, GBR) Mysterious duality (Abstract) 24. März A. Frühbis-Krüger Zeta-functions for families of Calabi-Yau n-folds with singularities (Abstract) 7. April 16:00 - 17:30 R. N. Kloosterman (HU Berlin) Mordell-Weil groups, Syzygies and Brill-Noether theory (Abstract) 11. April* S. Gährs A combinatorial approach to the Griffiths-Dwork method for invertible polynomials (Abstract) 14. April M. Verbitsky (Moskau, RUS) Global Torelli theorem for hyperkaehler manifolds and the mapping class group (Abstract) 21. April A. Apostolov Moduli spaces of IHS manifolds (Abstract) 28. April M. Bernardara (Essen) Derived categories of conic bundles (Abstract) 5. Mai X. Bogomolec Algorithmic normalization of arithmetic surfaces (Abstract) 19. Mai I. Kiming, Kopenhagen (DNK) On modular Galois representations modulo prime powers (Abstract) 26. Mai K. Oguiso (Osaka, JAP) Group of automorphisms of Wehler type on Calabi-Yau manifolds and compact hyperkaehler manifolds (Abstract) 9. Juni V. Alexeev (Univ. Georgia, USA) On the three compactifications of Siegel space (Abstract) 16. Juni M. Verbitsky (Moskau, RUS) An intrinsic volume functional on almost complex 6-manifolds and nearly Kaehler geometry (Abstract) 23. Juni F. Schulze Singular K3 surfaces with class number 2 (Abstract) 7. Juli W. Ebeling, S. M. Gusein-Zade (Moskau, RUS) Mirror symmetry of orbifold Landau-Ginzburg models (Abstract) 14. Juli M. Joumaah Finite order automorphisms of irreducible symplectic manifolds (Abstract) Anmerkungen * Dieser Termin findet von 16:15-17:45 in Raum g117 statt.

 WiSe 2010/11 Datum Vortragender Titel 14. Oktober* 15:15-16:45 C. Peters (Grenoble, FRA) Abelian fourfolds of Weil type and special K3 double planes (Abstract) 21. Oktober S. N. Kadir Motivic singularity conjectures (Abstract) 28. Oktober M. Wandel Moduli spaces of stable pairs in Donaldson-Thomas theory (Abstract) 1. November** C. Liedtke (Stanford, USA) On the birational nature of lifting (Abstract) 4. November 14:00-18:00 3. NTH-Computeralgebra Tag Braunschweig - Hannover 11. November K. Hulek Moduli von O'Grady Mannigfaltigkeiten (Abstract) 15. November fällt aus N. Budur (Notre Dame, USA) Local systems and singularities (Abstract) 25. November M. R. Blanco (Cuenca, ESP) A new desingularization algorithm for binomial varieties in arbitrary characteristic (Abstract) 2. Dezember J. Stix (Heidelberg) On the passage form local to global in Grothendieck's section conjecture (Abstract) 9. Dezember A. Prendergast - Smith The cone conjecture for abelian varieties (Abstract) 13. Dezember** K. Arzdorf An Algorithmic Approach to Semistable Reduction (Abstract) 6. Januar O. Tommasi Orbifold cohomology of the moduli space of curves of genus 3 (Abstract) 13. Januar L. H. Halle (Oslo, NOR) Degenerations of Calabi-Yau varieties, and the motivic monodromy conjecture (Abstract) 20. Januar S. Krug Orbifold Cohomology of M1,n and R1,n (Abstract) 27. Januar G. Hein (Essen) From quadratic forms to modular forms (Abstract) 31. Januar*** A. Sarti (Poitiers, FRA) Enriques-Flächen (Abstract) 3. Februar A. Schweizer (Taipei, TWN) Der Bruhat-Tits Baum und elliptische Kurven über Fq(t) Anmerkungen * Dieser Termin findet von 15:15-16:45 in Raum a410 statt. ** Die Termine am 1.11., 15.11. und 13.12 finden von 16:15-17:45 in Raum g123 statt. *** Der Termin am Montag, 31.1.findet von 14:15-15:45 in Raum g117 statt.

 SoSe 2010 Datum Vortragender Titel 8. April V. Lazic (MPI Bonn) New outlook on Mori theory (Abstract) 15. April D. Ploog Equivariant Fourier-Mukai transforms and Hilbert schemes (Abstract) 22. April J. C. Rohde Generic Hodge groups and Calabi-Yau manifolds (Abstract) 27. April S. Maubach (Nijmegen, NED) Polynomial automorphisms and affine algebraic geometry 6. Mai A. D. Apostolov Monodromy Invariants for Polarized Symplectic Manifolds (Abstract) 20. Mai H. Hartmann (Bonn) Stability conditions on K3 surfaces near cusps of the Kaehler moduli space (Abstract) 26. Mai Gemeinsames NTH-Seminar Computeralgebra mit der TU Braunschweig 3. Juni S. Gährs Picard-Fuchs Equations of Arnolds strange duality (Abstract) Montag, 7. Juni, 14:15 - 15:15, Raum a 310: M. Joumaah Linearsysteme auf Enriquesflächen (Abstract) 10. Juni A. Obus (Columbia, USA) Ramification in Fields of Moduli (Abstract) Montag, 21. Juni, 14:15 - 15:45, Raum a 310: S. M. Gusein-Zade (Moskau) On generating series of classes of equivariant Hilbert schemes of fat points (Abstract) 24. Juni N. Broomhead Autoequivalences of toric surfaces (Abstract) Dienstag, 29. Juni, 15:15-16:45, Raum a410 A. Stein (Oldenburg) Ellipic Curves and Cryptography - Some (new) attacks to the elliptic curve discrete logarithm problem (Abstract) 1. Juli C. Schoen (Duke/MPI Bonn) A numerical look at the generalized Birch and Swinnerton-Dyer conjecture (Abstract) Dienstag, 6. Juli 15:15-16:45, Raum a410 Sefi Ladkani (IHES, FRA) Perverse equivalences, mutations and applications 8. Juli M. Guldbrandsen (Haugesund, NOR) Obstruction theory for perfect complexes on abelian threefolds (Abstract) Montag, 12. Juli, 13:15-15:30, Raum f128 13:15-14:15 H. Ohashi (RIMS, JAP) Hutchinson-Weber involutions degenerate exactly when the Jacobian is Comessatti (Abstract) Montag, 12. Juli, 13:15-15:30, Raum f128 14:30-15:30 S. Kondo (Nagoya, JAP) The Segre cubic, the Igusa quartic and Borcherds products (Abstract) Montag, 19. Juli, 16:00-18:00, Raum f107: Tetsuji Shioda (Rikkyo/RIMS, JAP) Galois representations and Mordell-Weil lattices (Abstract) Dienstag, 20. Juli, 16:00-18:00, Raum f107: N. D. Elkies (Harvard, USA) On the areas of rational triangles (Abstract) 26. August S. Lin (Berkeley, USA) Asymptotic Approximation of Marginal Likelihood Integrals (Abstract)

 WiSe 2009/10 Datum Vortragender Titel 8. Oktober A. Prendergast -Smith The cone conjecture for some rational elliptic threefolds (Abstract) 15. Oktober S. Wewers Resolution of quotient singularities and stable reduction 29. Oktober I. Dan-Cohen (UC Berkeley, USA) Moduli of unipotent representations in characteristic 0 (Abstract) 5. November L. H. Halle Behaviour of component groups of Neron models under ramified extensions (Abstract) 12. November U. Schlickewei (Bonn) K3 surfaces with real multiplication and the Hodge conjecture (Abstract) 24. November* B. Hovinen The Open Swallowtail as a Matrix-Factorisation (Abstract) 3. Dezember R. N. Kloosterman (HU Berlin) The average rank of elliptic n-folds (Abstract) 10. Dezember J. Cerviño (Essen) Gitter-Invarianten (Abstract) 17. Dezember O. Tommasi Towards a computation of the cohomology of the moduli space of abelian fourfolds (Abstract) 7. Januar S. Krug Rational Cohomology of S2 and R2 (Abstract) 14. Januar 14:00-18:00 Gemeinsames NTH-Seminar Computeralgebra mit der TU Braunschweig 28. Januar A. Garbagnati (Milano, ITA) Elliptic K3 surfaces with abelian and dihedral groups of symplectic automorphisms (Abstract) 2. Februar* A. Takahashi (Osaka, JAP) GW invariants for weighted projective lines mirror dual to simple elliptic singularities (Abstract) 15. Februar** E. Markman (Amherst, USA) The Beauville-Bogomolov class as a characteristic class (Abstract) Anmerkungen * Diese Termine finden am Dienstag von 16:15-17:45 in Raum f309 statt. ** Der Termin findet am Montag, 15.2.2010 von 16:15-17:45 in Raum g117 statt.

 SoSe 2009 Datum Vortragender Titel 2. April A. Frühbis-Krüger Desingularization in positive characteristic, kangaroo points and obstacles to generalizing the Hauser- Wagner approach to dimension 3 (Abstract) 9. April M. Dettweiler (Heidelberg) The arithmetic of rigid local systems 16. April N. Behrens Compactification of ball quotients and singularities 30. April J. C. Rohde Maximal automorphisms of Calabi-Yau manifolds versus maximally unipotent monodromy (Abstract) 7. Mai S. M. Gusein-Zade (Moscow) Poincaré series of collections of plane valuations (Abstract) 14. Mai N. Broomhead Dimer models and consistency 20. Mai* D. Ploog (Toronto, CAN) Triangulated categories of singularities (Abstract) 28. Mai S. H. Weintraub (Göttingen/Lehigh) Involutionen, Humbertsche Flächen und Divisoren auf einem Modulraum (Abstract) 15. Juni** F. Vallentin (TU Delft, NED) Covering maxima 18. Juni J. Bergström (U. v. Amsterdam, NED) Cohomology of local systems on the moduli space of abelian threefolds (Abstract) 25. Juni P. Newstead (Liverpool, GBR) Clifford indices for vector bundles on curves 2. Juli O. Labs (Saarbrücken) Reelle Flächen mit Singularitäten und deren Visualisierung Anmerkungen * Der Termin am Mittwoch, 20.5.2009 findet von 16:30-18:00 im Raum g123 statt. ** Der Termin am Montag, 15.6.2009 findet von 15:30-17:00 im Raum g117 statt.

 WiSe 2008/09 Datum Vortragender Titel 9. Oktober W. Ebeling Über Indizes von 1-Formen auf determinantiellen Singularitäten 16. Oktober D. Ploog Vorbesprechung Seminar Landau-Ginzburg-Modelle und Matrixfaktorisierung 6. November A. du Plessis (Aarhus, DEN) Stratifying spaces of smooth maps 13. November U. Hartl (Münster) Elliptische Kurven und Drinfeld-Moduln (Abstract) 27. November N. Pagani (Sissa, ITA) The orbifold tautological ring for moduli of genus 1 curves (Abstract) 11. Dezember D. Ploog Homological Mirror Symmetry in the simplest case: elliptic curves (Abstract) 15. Dezember* K. Werner Quadratische Formen für die einfachen Raumkurvensingularitäten 18. Dezember K. Arzdorf On Local Models with Special Parahoric Level Structure 8. Januar S. Krug Log-kanonische Modelle von Mg (1) 15. Januar O. Tommasi Log-kanonische Modelle von Mg (2) 22. Januar 17:30-19:00 K. Ludwig Log-kanonische Modelle von Mg (3) 29. Januar R. Kloosterman Computing the zeta function of hypersurfaces with defect (Abstract) Anmerkungen * Der Termin am Montag, 15.12.2008 findet von 16:15-17:45 im Raum G123 statt.

 SoSe 2008 Datum Vortragender Titel 10. April 16:15-17:45 S. M. Gusein-Zade (Moskau) Power structure over the Grothendieck ring of varieties and its applications 17. April O. Tommasi On hypersurfaces with too many lines (Abstract) 24. April K. Hulek The Mordell-Weil rank of elliptic threefolds 8. Mai G. Wiese (Essen) Anwendung von Modulformen in inverser Galois-Theorie 29. Mai Y. Nagai (Mainz) On monodromies of a degeneration of irreducible symplectic Kähler manifolds (Abstract) 5. Juni U. Kühn (Hamburg) Explizite Berechnungen von arithmetischen Schnittzahlen 12. Juni M. Schütt (Harvard) K3 surfaces of Picard rank 20 (Abstract) 26. Juni H. Sander Der Satz von Torelli für irreduzible symplektische Mannigfaltigkeiten 3. Juli N. Behrens Kanonische Singularitäten bei speziellen Ballquotienten 17. Juli D. Ploog Fourier–Mukai-Partner von K3-Flächen

 WiSe 2007/08 Datum Vortragender Titel 11. Oktober D. Ploog Postnikov-Stabilität von Komplexen 18. Oktober S. Elsenhans Die Anzahl rationaler Punkte auf Varietäten &mdash die Manin-Vemutung 25. Oktober D. Ploog Derivierte Kategorien in der Algebraischen Geometrie (1) 1. November A. Frühbis-Krüger Algorithmische Auflösung von Singularitäten in Charakteristik 0 8. November D. Ploog Derivierte Kategorien in der Algebraischen Geometrie (2) 15. November I. Bouw (Ulm) Ganzzahlige Lösungen von Differentialgleichungen und Teichmüller-Kurven 22. November K. Wendland (Augsburg) On K3 surfaces and beyond &mdash from a geometer's and a conformal field theorist's point of view (Abstract) 6. Dezember S. Kadir Ganzzahligkeit von Instanton-Zahlen: Physik und Hodge-Theorie 13. Dezember O. Tommasi Ganzzahligkeit von Instanton-Zahlen: p-adische Hodge-Theorie 20. Dezember R. Kloosterman Ganzzahligkeit von Instanton-Zahlen: Motive und Integralitätsbeweis 10. Januar M. Schütt (Harvard) K3-Flächen und Modulformen (Abstract) 17. Januar S. Wewers Hyperbolizität (1) 24. Januar S. Wewers Hyperbolizität (2)