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Spring Semester 2017
Note: The highlighted event marks the next occurring event and events marked with an asterisk (*) indicate that the time and/or location are different from the usual time and/or location.
Date / Time  Speaker  Title  Location  

22 February 2017 13:3015:00 
Dr. Hyenho Lho ETH Zürich 
GW/SQ wall crossing I  HG G 43  
Abstract: We will study the wall crossing formula between GromovWitten invariant and Stable Quotient invariant for all genus. This formula which is recently proved for very general cases by CiocanFontanine and Kim cover large class of target spaces. In a series of lectures, we will study this formula eventually enlarging the class of target spaces from Fano to CalabiYau.  
24 February 2017 16:0017:15 
Dr. Enrica Floris Universität Basel 
Invariance of plurigenera for foliations on surfaces  HG G 43  
Abstract: Recently, Brunella and McQuillan proved some of the main results of birational geometry in the setup of foliations on surfaces. In this talk, we will discuss to which extent the theorem of Invariance of Plurigenera is true for foliations on surfaces. This is a joint work with Paolo Cascini.  
1 March 2017 13:3015:00 
Dr. Hyenho Lho ETH Zürich 
GW/SQ wall crossing II  HG G 43  
Abstract: We will study the wall crossing formula between GromovWitten invariant and Stable Quotient invariant for all genus. This formula which is recently proved for very general cases by CiocanFontanine and Kim cover a large class of target spaces. In series of lectures, we will study this formula eventually enlarging the class of target spaces from Fano to CalabiYau.  
3 March 2017 16:0017:15 
Pierrick Bousseau Imperial College London 
DT invariants from holomorphic curves  HG G 43  
Abstract: I will first describe a general analogy between DT invariants of 3CalabiYau categories and holomorphic disks in holomorphic symplectic varieties, and reinterpret the GromovWitten/Kronecker correspondence in this context. In some specific case, I will then explain a conjectural extension of this result relating refined DT invariants and holomorphic curves of higher genus. Finally, I plan to give a sketch of proof of this extended correspondence.  
8 March 2017 13:3015:00 
Dr. Hyenho Lho ETH Zürich 
GW/SQ wall crossing III  HG G 43  
Abstract: We will study the wall crossing formula between GromovWitten invariant and Stable Quotient invariant for all genus. This formula which is recently proved for very general cases by CiocanFontanine and Kim cover a large class of target spaces. In series of lectures, we will study this formula eventually enlarging the class of target spaces from Fano to CalabiYau.  
15 March 2017 13:3015:00 
Dr. Hyenho Lho ETH Zürich 
GW/SQ wall crossing IV  HG G 43  
Abstract: We will study the wall crossing formula between GromovWitten invariant and Stable Quotient invariant for all genus. This formula which is recently proved for very general cases by CiocanFontanine and Kim cover a large class of target spaces. In series of lectures, we will study this formula eventually enlarging the class of target spaces from Fano to CalabiYau.  
17 March 2017 16:0017:15 
Prof. Dr. Filippo Viviani Roma III 
The cohomology of the Hilbert schemes and of the compactified Jacobians of a singular curve  HG G 43  
Abstract: We generalize the classical MacDonald formula for smooth curves to reduced curves with planar singularities. More precisely, we show that the cohomologies of the Hilbert schemes of points on a such a curve are encoded in the cohomologies of the fine compactified Jacobians of its connected subcurves, via the perverse Leray filtration. This is a joint work with Luca Migliorini and Vivek Shende.  
22 March 2017 13:3015:00 
Dr. Tyler Kelly University of Cambridge 
A toric Orlov theorem via LandauGinzburg models  HG G 43  
Abstract: Orlov's theorem defines and proves that any smooth Fano (resp. general type) hypersurface in projective nspace has a subcategory (resp. supercategory) in its bounded derived category of coherent sheaves that is a Fractional CalabiYau category. We prove this is the case for a certain class of toric complete intersections. The method to find this is by studying a LandauGinzburg model associated to the toric complete intersection and then using geometric invariant theory. We will try to focus on studying a few motivating examples from previous literature. This work is joint with David Favero (Alberta).  
24 March 2017 16:0017:15 
Dr. Olivier Benoist Université de Strasbourg 
Sums of squares on real uniruled varieties  HG G 43  
Abstract: It is a classical theorem of Pfister that a nonnegative rational function on a real algebraic variety of dimension n is a sum of 2^n squares. In this talk, we will investigate improvements on this bound under additional geometric hypotheses. Here is an example of the results we will explain: in the function field of a real uniruled threefold without real points, 1 is a sum of 4 squares. This is partly joint work with Olivier Wittenberg.  
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31 March 2017 16:3017:45 
Jason van Zelm University of Liverpool 
Nontautological bielliptic cycles  HG G 43  
Abstract: Tautological classes are geometrically defined classes in the Chow ring of the moduli space of curves which are particularly well understood. The classes of many known geometrically defined loci were proven to be tautological. A bielliptic curve is a curve with a 2to1 map to an elliptic curve. In this talk we will build on an idea of Graber and Pandharipande to show that the closure of the locus of bielliptic curves in the moduli space of stable curves of genus g is nontautological when g is at least 12.  
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11 April 2017 13:0014:15 
Prof. Dr. Sergey Shadrin University of Amsterdam 
The tautological ring of M_{g,n} via PandharipandePixtonZvonkine rspin relations  HG G 19.1  
Abstract: We use relations in the tautological ring of the moduli spaces \bar{M}_{g,n} derived by Pandharipande, Pixton, and Zvonkine from the Givental formula for the rspin Witten class in order to obtain some restrictions on the dimensions of the tautological rings of the open moduli spaces M_{g,n}. In particular, we give a new proof for the result of Looijenga (for n=1) and Buryak et al. (for n>= 2) that dim R^{g1}(M_{g,n})<= n. We also give a new proof of the result of Looijenga (for n=1) and Ionel (for arbitrary n>= 1) that R^i(M_{g,n})=0 for i>= g and give some estimates for the dimension of R^i(M_{g,n}) for $i<= g2.  
26 April 2017 13:3015:00 
Dr. Clément Dupont Université de Montpellier 
Brown's moduli spaces of curves and the gravity operad  HG G 43  
Abstract: We will introduce Brown’s moduli spaces, which parametrize genus zero curves. The original motivation is arithmetic and lies in the algebrogeometric study of multiple zeta values. In this talk we will see how these spaces fit in the study of the operadic structures underlying the moduli spaces of genus zero curves. More precisely, we will explain the proof of two essentially equivalent results: the purity of the Hodge structure on the cohomology of Brown’s moduli spaces, and the freeness of the non symmetric operad underlying Getzler’s gravity operad. This is joint work with Bruno Vallette.  
5 May 2017 16:0017:15 
Dr. Honglu Fan ETH Zürich 
GromovWitten theory of projective bundles  HG G 43  
Abstract: Originally motivated by the crepant transformation conjecture for ordinary flops, we tried to study how much can characteristic classes determine the GromovWitten theory of projective bundles. I will talk about an easy example and our results. If there is time, I will also discuss some further ideas.  
10 May 2017 13:3015:00 
Dr. Nicola Tarasca University of Georgia 
Hyperelliptic loci in moduli spaces of curves  HG G 43  
Abstract: In this talk, I will discuss some recent results in the enumerative geometry of subvarieties of moduli spaces of curves. In joint work with Dawei Chen, we study the extremality of loci of hyperelliptic curves with marked Weierstrass points inside cones of effective classes of high codimension. I will present a formula for classes of loci of genustwo curves with marked Weierstrass points as result of an ongoing work with Renzo Cavalieri. These are among the first results toward the study of cones of higher codimensional effective classes.  
12 May 2017 16:0017:15 
Prof. Dr. Alexander Kuznetsov Steklov Mathematical Institute 
Derived categories of families of sextic del Pezzo surfaces  HG G 43  
Abstract: I will give a description of the derived category of coherent sheaves on a flat family of normal sextic del Pezzo surfaces with du Val singularities.  
17 May 2017 13:3015:00 
Junliang Shen ETH Zürich 
Derived categories of K3 surfaces, O'Grady's filtration, and Hyperkähler varieties  HG G 43  
Abstract: We discuss the connections among derived categories of K3 surfaces, O'Grady's filtration on Chow groups, and zero cycles on certain Hyperkähler varieties. First, we show that the second Chern class of any object in the derived category of a K3 surface lies in a suitable piece of O'Grady's filtration. This solves and generalizes a conjecture by O'Grady, and provides new structures on derived categories of K3 surfaces. Second, we introduce a conjecture concerning stable objects in derived categories of K3 surfaces and zero cycles on their moduli spaces. We show that our results and conjecture lead to a natural candidate of the BeauvilleVoisin filtration for zero cycles on these moduli spaces (which are Hyperkähler varieties of K3^[n]type). In particular, we will discuss its connection with Voisin's recent proposal via constant cycle subvarieties. This is based on a joint work with Qizheng Yin and Xiaolei Zhao.  
19 May 2017 16:0017:15 
Prof. Dr. Andrei Okounkov Columbia University 
Quasimap counts and integral solutions of the quantum KnizhnikZamolodchikov equations  HG G 43  
Abstract: I will review the appearance of qKZ and related difference equations in the enumerative Ktheory of quasimaps to Nakajima varieties and explain, following a joint paper with Mina Aganagic, how a correspondence between descendent and relative enumerative constraints translates into MellinBarnes integral formulas for solutions. The example of the Hilbert schemes of points in C^2 will be emphasized throughout the talk.  
24 May 2017 13:3015:00 
Dr. Nicola Tarasca Univ. of Georgia 
Kclasses of BrillNoether loci and a determinantal formula  HG G 43  
Abstract: I will present a formula for the Euler characteristic of the structure sheaf of BrillNoether loci of linear series on curves with prescribed vanishing at marked points. The formula recovers the classical Castelnuovo number in the zerodimensional case, and previous results of EisenbudHarris, Pirola, ChanLópezPfluegerTeixidor in the curve case. The result follows from a new determinantal formula for the Ktheory class of certain degeneracy loci of maps of flag bundles. This is joint work with Dave Anderson and Linda Chen.  
23 June 2017 16:0017:15 
Dr. Hyenho Lho ETH Zürich 
Vanishing condition on the GW invariants of P1^n  HG G 43  
Abstract: We will prove some vanishing conditions of GromovWitten invariants of product of projective lines.  
*
27 June 2017 13:3014:45 
Dr. Georg Oberdieck MIT 
Holomorphic anomaly equations for elliptic fibrations  HG G 19.2  
Abstract: The GromovWitten potentials of an elliptic curve are known to be quasimodular forms and to satisfy a holomorphic anomaly equation (HAE), a recursive formula for the derivative with respect to the second Eisenstein series. We explain a conjectural HAE for general elliptic fibrations and present some evidence along the way. This is joint work with Aaron Pixton.  
*
27 June 2017 15:1516:30 
Dr. Qingtao Chen ETH Zürich 
Recent progress of various Volume Conjectures for links as well as 3manifolds  HG G 19.2  
Abstract: The original Volume Conjecture of KashaevMurakamiMurakami predicts a precise relation between the asymptotics of the colored Jones polynomials of a knot in S^3 and the hyperbolic volume of its complement. I will discuss two different directions that lead to generalizations of this conjecture. The first direction concerns different quantum invariants of knots, arising from the colored SU(n) (with the colored Jones polynomial corresponding to the case n = 2). I will first display subtle relations between congruence relations (inspired by large N duality relating ChernSimons gauge theory and GromovWitten theory), cyclotomic expansions and the original Volume Conjecture for colored Jones polynomials of knots. I will then generalize this point of view to the colored SU(n) invariant of knots. Certain congruence relations for colored SU(n) invariants, discovered in joint work with K. Liu, P. Peng and S. Zhu, lead us to formulate cyclotomic expansions and a Volume Conjecture for these colored SU(n) invariants. If time permits, I will briefly discuss similar ideas for the superpolynomials that arise in HOMFLYPT homology. Another direction for generalization involves the WittenReshetikhinTuraev and (modified) TuraevViro quantum invariants of 3manifolds. In a joint work with T. Yang, we formulated a new Volume Conjecture for the asymptotics of these 3manifolds invariants evaluated at certain roots of unit, and numerically checked it for many examples. I would like report current situation of these new conjectures, which include my new work with Jun Murakami. Interestingly, this conjecture uses roots of unity that are different from the one usually considered in literature. This may indicate that the understanding of this new phenomenon requires new physical and geometric interpretations that go beyond the usual quantum ChernSimons theory. 
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