From April 29 to May 1, 2019 the CMSA will be hosting a Conference on Algebraic Geometry, Representation theory and Mathematical Physics. This workshop is organized by Bong Lian (Brandeis) and Artan Sheshmani (CMSA) . The workshop will be held in room G10 of the CMSA, located at 20 Garden Street, Cambridge, MA.
For a list of lodging options convenient to the Center, please visit our recommended lodgings page.
Monday, April 29
Time 
Speaker 
Title/Abstract 
8:30 – 9:00am 
Breakfast 

9:00 – 10:00am 
Wei Zhang, MIT 
Title: The arithmetic fundamental lemma for diagonal cycles Abstract: I’ll recall the Gross–Zagier theorem and a high dimensional generalization, the arithmetic GanGrossPrasad conjecture, which relates the height pairing of arithmetic diagonal cycles on certain shimura varieties to the first order derivative of certain Lfunctions. The arithmetic fundamental lemma conjecture arises from the relative trace formula approach to this conjecture. I will recall the statement of the arithmetic fundamental lemma and outline a proof. 
10:00 – 10:30am 
Break 

10:30 – 11:30am 
Yuri Tschinkel, NYU 
Title: Equivariant birational geometry and modular symbols Abstract: We introduce new invariants in equivariant birational geometry and study their relation to modular symbols and cohomology of arithmetic groups (joint with M. Kontsevich and V. Pestun). 
11:30 – 1:30pm 
Lunch 

1:30 – 2:30pm 
Alexander Efimov, Moscow 
Title: Torsionness for regulators of canonical extensions Abstract: I will sketch a generalization of the results of Iyer and Simpson arXiv:0707.0372 to the general case of a normalcrossings divisor at infinity. 
2:30 – 3:00pm 
Break 

3:00 – 4:00pm 
Amin Gholampour, Maryland 
Title: Euler Characteristics of punctual quot schemes on threefolds Abstract: Let F be a homological dimension 1 torsion free sheaf on a nonsingular quasiprojective threefold. The first cohomology of the derived dual of F is a 1dimension sheaf G supported on the singular locus of F. We prove a wallcrossing formula relating the generating series of the Euler characteristics of Quot(F, n) and Quot(G,n), where Quot(,n) denotes the quot scheme of length n quotients. We will use this relation in studying the Euler characteristics of the moduli spaces of stable torsion free sheaves on nonsingular projective threefolds. This is a joint work with Martijn Kool. 
4:00 – 4:30pm 
Break 

4:30 – 5:30pm 
Maksym Fedorchuck, BC 
Title: Stability of oneparameter families of weighted hypersurfaces Abstract: We define a notion of stability for fibrations over a curve with generic fibers being weighted hypersurfaces (in some weighted projective space) generalizing Kollár’s stability for families of hypersurfaces in a projective space. The stability depends on a choice of an effective line bundle on the parameter space of weighted hypersurfaces and different choices pick out different birational model of the total space of the fibration. I will describe enumerative geometry that goes into understanding these stability conditions, and, if time permits, examples where this machinery can be used to produce birational models with good properties. Joint work with Hamid Ahmadinezhad and Igor Krylov. 
Tuesday, April 30
Time 
Speaker 
Title/Abstract 
8:30 – 9:00am 
Breakfast 

9:00 – 10:00am 
Brendan Hassett, Brown 
Title: Rationality for geometrically rational threefolds Abstract: We consider rationality questions for varieties over nonclosed fields that become rational over an algebraic closure, like smooth complete intersections of two quadrics. (joint with Tschinkel) 
10:00 – 10:30am 
Break 

10:30 – 11:30am 
Dennis Gaitsgory, Harvard 
Title: The Fundamental Local Equivalence in quantum geometric Langlands Abstract: The Fundamental Local Equivalence is statement that relates the qtwisted Whittaker category of the affine Grassmannian for the group G and the category of modules over the Langlands dual “big” quantum group. The nontriviaiity of the statement lies is the fact that the relationship between the group and its dual is combinatorial, so to prove the FLE one needs to express both sides in combinatorial terms. In the talk we will indicate the proof of a related statement for the “small” quantum group. The combinatorial link is provided by the category of factorization modules over a certain factorization algebra, which in itself is a geometric device that concisely encodes the root data. 
11:30 – 1:00pm 
Lunch 

1:00 2:00pm 
Andrei Negut, MIT 
Title: AGT relations in geometric representation theory Abstract: I will survey a program that seeks to translate the AldayGaiottoTachikawa correspondence (between gauge theory on R^4 and conformal field theory) into the language of algebraic geometry. The objects of study become moduli spaces of sheaves on surfaces, and the goal is to connect them with the Walgebra of type gl_n. 
2:00 – 2:15pm 
Break 

2:15 – 3:15pm 
Dan Abramovich, Brown 
Title: Resolution in characteristic 0 using weighted blowing up Abstract: Given a variety $X$, one wants to blow up the worst singular locus, show that it gets better, and iterate until the singularities are resolved. Examples such as the whitney umbrella show that this iterative process cannot be done by blowing up smooth loci – it goes into a loop. We show that there is a functorial way to resolve varieties using \emph{weighted} blowings up, in the stacktheoretic sense. To an embedded variety $X \subset Y$ one functorially assigns an invariant $(a_1,\ldots,a_k)$, and a center locally of the form $(x_1^{a_1} , \ldots , x_k^{a_k})$, whose stacktheoretic weighted blowing up has strictly smaller invariant under the lexicographic order. This is joint work with Michael Tëmkin (Jerusalem) and Jaroslaw Wlodarczyk (Purdue), a side product of our work on functorial semistable reduction. A similar result was discovered by G. Marzo and M. McQuillan. 
3:15 – 3:30pm 
Break 

3:30 – 4:30pm 
Fedor Bogomolov, NYU 
Title: On the base of a Lagrangian fibration for a compact hyperkahler manifold. Abstract: In my talk I will discuss our proof with N. Kurnosov that the base of such fibration for complex projective manifold hyperkahler manifold of dimension $4$ is always a projective plane $P^2$. In fact we show that the base of such fibration can not have a singular point of type $E_8$. It was by the theorem of Matsushita and others that only quotient singularities can occur and if the base is smooth then the it is isomorphic to $P^2$. The absence of other singularities apart from $E_8$ has been already known and we show that $E8$ can not occur either. Our method can be applied to other types of singularities for the study of Lagrangian fibrations in higher dimensions More recently similar result was obtained by Huybrechts and Xu. 
4:30 – 4:45pm 
Break 

4:45 – 5:45pm 
Dawei Chen, BC 
Title: Volumes and intersection theory on moduli spaces of Abelian differentials Abstract: Computing volumes of moduli spaces has significance in many fields. For instance, Witten’s conjecture regarding intersection numbers on moduli spaces of Riemann surfaces has a fascinating connection to the WeilPetersson volume, which motivated Mirzakhani to give a proof via Teichmueller theory, hyperbolic geometry, and symplectic geometry. In this talk I will introduce an analogue of Witten’s intersection numbers on moduli spaces of Abelian differentials to compute the MasurVeech volumes induced by the flat metric associated with Abelian differentials. This is joint work with Moeller, Sauvaget, and Zagier (arXiv:1901.01785). 
Wednesday, May 1
Time 
Speaker 
Title/Abstract 
8:30 – 9:00am 
Breakfast 

9:00 – 10:00am 
Pavel Etingof, MIT 
Title: Short starproducts for filtered quantizations Abstract: PDF This is joint work with Eric Rains and Douglas Stryker. 
10:00 – 10:30am 
Break 

10:30 – 11:30am 
Roman Bezrukavnikov, MIT 
Title: Stability conditions and representation theory Abstract: I will recall the concept of real variation of stabilities (introduced in my work with Anno and Mirkovic) 
11:30 – 11:45am 
Break 

11:45 – 12:45pm 
Qile Chen, BC 
Title: Counting curves in critical locus via logarithmic compactification Abstract: An Rmap consists of a prestable map to possibly nonGIT quotient together with sections of certain spin bundles. The moduli of Rmaps are in general noncompact. When the target of Rmaps is equipped with a superpotential W with compact critical locus, using KiemLi cosection localization it has been proved by many authors in various settings that the virtual cycle of Rmaps can be represented by the cosection localized virtual cycle which is supported on the proper locus consisting of Rmaps in the critical locus of W. Though the moduli of Rmaps is equipped with a natural torus action by scaling of the spin bundles, the noncompactness of the Rmaps moduli makes such powerful torus action useless. In this talk, I will introduce a logarithmic compactification of the moduli of Rmaps using certain modifications of stable logarithmic maps. The logarithmic moduli space carries a canonical virtual cycle from the logarithmic deformation theory. In the presence of a superpotential with compact critical locus, it further carries a reduced virtual cycle. We prove that (1) the reduced virtual cycle of the compactification can be represented by the cosection localized virtual cycle; and (2) the difference of the canonical and reduced virtual cycles is another reduced virtual cycle supported along the logarithmic boundary. As an application, one recovers the GromovWitten invariants of the critical locus as the invariants of logarithmic Rmaps of its ambient space in an explicit form. The latter can be calculated using the spin torus action. This is a joint work with Felix Janda and Yongbin Ruan. 
12:45 – 2:30pm 
Lunch 

2:30 – 3:30pm 
Si Li, Tsinghua 
Title: Semiinfinite Hodge structure: from BCOV theory to SeibergWitten geometry Abstract: I will explain how the semiinfinite Hodge theory extends KodairaSpencer gravity (BershadskyCecottiOoguriVafa theory of Btwisted closed topological string field theory) into a full solution of BatalinVilkovisky master equation. This allows us to formulate quantum Bmodel via a rigorous BV quantization method and construct integrable hierarchies arising naturally from the background symmetry. In the second part of the talk, I will explain the recent discovery of the connection between K.Saito’s primitive form and 4d N=2 SeibergWitten geometry arising from singularity theory. 
3:30 – 4:00pm 
Break 

4:00 – 5:00pm 
Ludmil Katzarkov, Moscow 
Title: PDE’s non commutative motives and HMS. Abstract: In this talk we will discuss the theory of central manifolds and the new structures in geometry it produces. Application to Bir. Geometry will be discussed. 