# SCIENTIFIC PROGRAMS AND ACTIVITIES

December 11, 2016
THE FIELDS INSTITUTE FOR RESEARCH IN MATHEMATICAL SCIENCES
 Thematic Program on Calabi-Yau Varieties: Arithmetic, Geometry and Physics October 15-19, 2013 Workshop 2 on Enumerative geometry and Calabi–Yau varieties Principal Organizers: Mark Gross, Radu Laza, Jaume Gomis, Shing-Tung Yau Note: Workshops 2 & 3 will be organized jointly with the Perimeter Institute. In order to ease participation in both workshops, they will be held back-to-back, one at the Fields Institute and the other at the Perimeter Institute. October 21-25, 2013 to be held at the Perimeter Institute Workshop 3 on Physics around Mirror Symmetry Principal Organizers: Vincent Bouchard, Jaume Gomis, Sergei Gukov, Johannes Walcher, Shing-Tung Yau.
 Confirmed Participants Concentrated Graduate Course Speaker and Talk Info Back to main index

Preliminary Schedule as of October 2

 October 15 Tuesday October 16 Wednesday October 17 Thursday October 18 Friday October 19 Saturday 9:30-10:30 Diaconescu, Duiliu, E. Parabolic refined invariants and Macdonald polynomials 11:00–12:00 Costello, Kevin Quantization of BCOV theory on Calabi-Yau manifolds Filippini, Sara Refined curve counting and wall-crossing Zaslow, Eric Legendrian Knots and Constructible Sheaves 14:00–15:00 Abouzaid, Mohammed Formality of Fukaya categories from disc counts 15:30–16:30 DLS (I) Kontsevich, Maxim What is tropical mathematics? DLS (II) Kontsevich, Maxim Quivers, cluster varieties and integrable systems DLS (III) Kontsevich, Maxim Fukaya category meets Bridgeland stability 17:00–19:00 DLS Reception

 Speaker Title and Abstract Abramovich, Dan Brown University Lecture Notes The decomposition formula for logarithmic Gromov-Witten invariants This is joint work of Qile Chen, Mark Gross, Bernd Siebert and me. A central aim of logarithmic Gromov–Witen theory is to find general formulas relating usual Gromov–Witten invariants of a smooth variety X with appropriate invariants of simpler varieties which appear as components of a degeneration of X. The first step is the decomposition formula, which breaks apart invariants of the singular fiber in combinatorial terms determined by tropical curves or graphs. I will describe our work on the decomposition formula, with examples (at least one example). Abouzaid, Mohammed Columbia University Formality of Fukaya categories from disc counts One of the main problems in computing Fukaya categories is to understand the underlying A-infinity structure even for simple and explicitly constructed Lagrangians. I will explain how one can use counts of holomorphic discs to prove the formality of certain (subcategories of) Fukaya categories, focusing on the example of the Milnor surfaces of type A. This is joint work with I. Smith. Brav, Chris IAS Hamiltonian local models for symplectic derived stacks We show that a derived stack with symplectic form of negative degree can be locally described in terms of generalised Darboux coordinates and a Hamiltonian cohomological vector field. As a consequence we see that the classical moduli stack of vector bundles on a Calabi–Yau threefold admits an atlas consisting of critical loci of regular functions on smooth varieties. If time permits, we discuss applications to the categorification of Donaldson–Thomas theory. This is joint work with subsets of Ben-Bassat, Bussi, Dupont, Joyce, and Szendroi. Bryan, Jim University of British Columbia ${\pi}$-stable pairs and the crepant resolution conjecture in Donaldson-Thomas theory We construct curve counting invariants for a Calabi–Yau threefold Y equipped with a dominant birational morphism ${\pi: Y \rightarrow X}$. Our invariants generalize the stable pair invariants of Pandharipande and Thomas which occur for the case when ${\pi: Y \rightarrow X}$ is the identity. In the case where ${\pi: Y \rightarrow X}$ is a semi-small crepant resolution, we prove a PT/DT - type formula relating the partition function of our invariants to the Donaldson-Thomas partition function. In the case where X is the coarse space of a Calabi–Yau orbifold, our partition function is equal to the Pandharipande–Thomas partition function of the orbifold. Our methods include defining a new notion of stability for sheaves which depends on the morphism ${\pi}$. Our notion generalizes slope stability which is recovered in the case where ${\pi}$ is the identity on Y . Chen, Qile Columbia University Very free curves on Fano complete intersection The theory of stable log maps are developed for studying the degeneration of Gromov–Witten invariants. In this talk, I will introduce another interesting application of stable log maps to classical birational geometry — we construct very free curves on Fano complete intersections in projective spaces over an algebraically closed field of arbitrary characteristics. This is a joint work with Yi Zhu. Cooper, Yaim Harvard University The geometry of stable quotient spaces in genus one Stable quotient spaces provide an alternative to stable maps for compactifying spaces of maps. In this talk I will discuss spaces of stable quotients which compactify the space of degree d maps of genus 1 curves to ${P^n}$. I will describe what is known about the geometry of these spaces. I will also discuss the relationship between these spaces and the corresponding spaces of stable maps from the perspective of the minimal model program. Costello, Kevin Northwestern University Quantization of BCOV theory on Calabi-Yau manifolds I’ll discuss some aspects of work in progress with Si Li on quantization of open and closed BCOV theory on Calabi-Yau manifolds. This gives a new formulation of the B-model which is local on the Calabi-Yau. If time permits, I’ll discuss some calculations in both the open and closed versions of this theory. Diaconescu, Duiliu, E. University of Alberta Parabolic refined invariants and Macdonald polynomials A string theoretic derivation is given for the conjecture of Hausel, Letellier and Rodriguez-Villegas on the cohomology of character varieties with marked points. Their formula is identified with a refined BPS expansion in the stable pair theory of a local root stack. Morever, Haiman’s geometric con- styruction for Macdonald polynomials is shown to emerge naturally in the context of geometric engineering. Filippini, Sarah Fields Institute Refined curve counting and wall-crossing The tropical vertex group of Kontsevich and Soibelman is generated by formal symplecto-morphisms of the 2-dimensional algebraic torus. It plays a role in many problems in algebraic geometry and mathematical physics. Based on the tropical vertex group, Gross, Pandharipande and Siebert introduced an interesting Gromov–Witten theory on weighted projective planes which admits a very special expansion in terms of tropical counts. I will describe a refinement or “q-deformation” of this expansion, motivated by wall-crossing ideas, using Block–Goettsche invariants. This leads naturally to the definition of a class of putative q-deformed curve counts. We prove that this coincides with another natural q-deformation, provided by a result of Reineke and Weist in the context of quiver representations, when the latter is well defined. Joint work with Jacopo Stoppa. Fukaya, Kenji Simons Institute Perturvation of constant maps, String topology and Perturbative Chern–Simons Theory In this talk I will explain the way to obtain a solution of certain master equation onthe cyclic bar complex of the de-Rhamcohomology. This solution is a constant map part of Lagrangian Floer theory and is related to the two stories in the title. Something new in this talk, which I will explain, is the way how to do it without using pseudoholomorphic curvein the cotangent bundle. So everything works in the story of finite dimensional spaces. However ‘virtual technique’ is used much. Gross, Mark UCSD Introduction to Logarithmic Gromov–Witten invariants Log Gromov–Witten invariants are a generalization of relative Gromov–Witten invariants. They can be used to define the notion of curve counts with specified tangencies along normal crossings divisors, or curve counts in normal crossings target spaces. I will outline the basic definitions of these invariants as developed by myself and Siebert, on the one hand, and Abramovich and Chen, on the other. Kontsevich, Maxim IHES Distinguished Lecture 1, What is tropical mathematics? In tropical mathematics the usual laws of algebra are changed, the subtraction is forbidden, the division is always permitted, and 1+1 is equal to 1. Analogs of usual geometric shapes like lines, circles etc. are replaced by new figures composed of pieces of lines. I will try to explain basics of tropical algebra and geometry, its relation with more traditional domains, and its role in mirror symmetry which is a remarkable duality originally discovered in string theory about 20 years ago. (II) Quivers, cluster varieties and integrable systems I’ll describe a new approach to cluster varieties and mutations based on scattering diagrams and wall-crossing formalism. The central role here is played by certain canonical transformation (formal change of coordinates) associated with arbitrary quiver. Also, a complex algebraic integrable system under some mild conditions produces a quiver, and the associated canonical transformation is a birational map. (III) Fukaya category meets Bridgeland stability Bridgeland’s notion of stability in triangulated categories is believed to be a mathematical encoding of D-branes in string theory. I’ll argue (using physics picture) that partially degenerating categories with stability should be described as a mixture between symplectic geometry and pure algebra. Spectral networks of Gaiotto, Moore and Neitzke appear as an example. Ruan, Yongbin Michigan University A mathematics theory of gauged linear sigma model Several years ago, we (Fan, Jarvis and myself) developed a theory for so called Landau-Ginzburg model. It has a variety of applications in integrable hierarchy, LG/CY correspondence and modularity. LG-model is a limit of so called gauged linear sigma model. In the talk, I will discuss a construction to generalize our ”classical” theory to the general situation of gauged linear sigma model. Some potential applications will be discussed. Ruddat, Helge Fields Institute Speculations on Mirror Symmetry for Riemann surfaces There has been quite some evidence that some form of mirror symmetry is valid for curves of higher genus. In known constructions, the dual geometry is derived from a higher-dimensional Landau–Ginzburg model. We present some ideas of how an intrinsic form of the mirror construction could be fomulated. Soibelman, Yan Kansas State University 3-dimensional Calabi-Yau manifolds and Hitchin integrable systems I am going to discuss the relationship between two topics mentioned in the title from the point of view of theory of Donaldson-Thomas invariants and wall-crossing formulas developed by Kontsevich and myself. Tseng, Hsian-Hua Ohio State University Mirror theorem, Seidel representation, and holomorphic disks The quantum cohomology ring QH*(X) of a projective toric manifold X can be computed in several ways. A presentation of QH*(X) can be derived from the toric mirror theorem of Givental, Lian-Liu-Yau, and Iritani. McDuff-Tolman use d Seidel representations to derive a presentation of QH*(X). More recently, Fukaya-Oh-Ohta-Ono showed that QH*(X) is isomorphic to the Jacobian ring of the Lagrangian Floer superpotential of X, which is defined in terms of counting of holomorphic disks in X. The purpose of this talk is to explain the geometric reason underlying the equivalence of these three seemingly very different approaches, when X is semi-Fano. Zinger, Alexsey Stony Brook Mirror Symmetry for Stable Quotients Invariants I will describe a mirror formula for the direct analogue of Givental’s J-function in the SQ theory. It is remarkably similar to the mirror formula in the Gromov–Witten theory, but the former does not involve a change of variables. This suggests that the mirror map relating the GW-invariants to the B-model of the mirror is more reflective of the choice of curve counting theory on the A side than of mirror symmetry. The proof of the mirror formula in the Fano case is as in the GW–theory. On the other hand, the proof in the Calabi–Yau case consists of showing that it is a consequence of the Fano case. This is joint work with Y. Cooper. Zaslow, Eric Northwestern University Legendrian knots and constructible sheaves Given a Legendrian knot, we construct a category, invariant under Legendrian isotopies up to equivalence. Rank-one objects of our category play a special role. On the one hand, they define a subcategory which we conjecture to be equivalent to the bilinearized Legendrian contact homology of the knot. On the other hand, the moduli of these objects is an interesting space which, for positive braid closures, enables one to recover the Khovanov–Rozansky categorified invariant of the topological type of the knot. I will try to explain all this by working through simple examples. This work is joint with Vivek Shende and David Treumann

Confirmed Participants to the Workshop as of October 9, 2013

 Full Name University/Affiliation Arrival Date Departure Date Abouzaid, Mohammed Columbia University 14-Oct-13 16-Oct-13 Abramovich, Daniel Brown University 14-Oct-13 20-Oct-13 Amir-Khosravi, Zavosh University of Toronto 01-Jul-13 30-Dec-13 Bertolini, Marco Duke University 14-Oct-13 26-Oct-13 Brav, Christopher Institute for Advanced Study 14-Oct-13 19-Oct-13 Bryan, Jim University of British Columbia 14-Oct-13 19-Oct-13 Ceballos, Cesar York University 13-Aug-13 20-Dec-13 Chan, Kwokwai The Chinese University of Hong Kong 13-Oct-13 20-Oct-13 Chen, Qile Columbia University 14-Oct-13 20-Oct-13 Cheung, Man-Wai UC San Diego 14-Oct-13 20-Oct-13 Costello, Kevin J Northwestern University 14-Oct-13 16-Oct-13 Dedieu, Thomas Université Paul Sabatier 06-Oct-13 20-Oct-13 Diaconescu, Duiliu-Emanuel University of Alberta 16-Oct-13 22-Oct-13 Fang, Bohan Columbia University 15-Oct-13 19-Oct-13 Filippini, Sara Angela Fields Institute 01-Jul-13 31-Dec-13 Fisher, Jonathan University of Toronto 01-Jul-13 31-Dec-13 Fukaya, Kenji Stony Brook University 16-Oct-13 20-Oct-13 Garcia-Raboso, Alberto University of Toronto 01-Aug-13 31-Dec-13 Gonzalez-Dorrego, Maria R. University of Toronto 16-Sep-13 19-Oct-13 Gross, Mark UC San Diego 14-Oct-13 20-Oct-13 Gualtieri, Marco University of Toronto 05-Sep-13 05-Dec-13 Jinzenji, Masao Hokkaido University 14-Oct-13 18-Oct-13 Karigiannis, Spiro University of Waterloo 15-Oct-13 19-Oct-13 Kasa, Michael UC San Diego 14-Oct-13 20-Oct-13 Kelly, Tyler University of Pennsylvania 15-Oct-13 19-Oct-13 Lau, Siu-Cheong Harvard University 15-Oct-13 19-Oct-13 Laza, Radu Stony Brook University 15-Oct-13 19-Oct-13 Li-Bland, David Berkeley 24-Sep-13 16-Oct-13 Marcus, Steffen University of Utah 11-Oct-13 18-Oct-13 Molnar, Alexander Queen's University 01-Jul-13 31-Dec-13 Moraru, Ruxandra University of Waterloo 15-Oct-13 19-Oct-13 Movasati, Hossein Instituto Nacional de Matemática Pura e Aplicada 15-Oct-13 22-Nov-13 Odaka, Yuji Imperial college (/Kyoto university) 14-Oct-13 18-Oct-13 Overholser, Douglas University of California, San Diego 01-Jul-13 31-Dec-13 Park, B. Doug University of Waterloo 01-Sep-13 20-Dec-13 Perunicic, Andrija Fields Institute 02-Jul-13 31-Dec-13 Quigley, Callum University of Alberta 10-Oct-13 25-Oct-13 Rayan, Steven University of Toronto 15-Jun-13 30-Jan-14 Rose, Simon Fields Institute 01-Jul-13 31-Dec-13 Ross, Dustin University of Michigan 14-Oct-13 19-Oct-13 Ruan, Yongbin University of Michigan 15-Oct-13 19-Oct-13 Ruddat, Helge Universität Mainz 25-Jun-13 31-Dec-13 Schaug, Andrew University of Michigan 15-Sep-13 20-Oct-13 Selmani, Sam McGill University 15-Sep-13 20-Nov-13 Silversmith, Robert University of Michigan 14-Oct-13 20-Oct-13 Soibelman, Yan Kansas State University 14-Oct-13 26-Oct-13 Soloviev, Fedor University of Toronto 01-Jul-13 30-Dec-13 Thompson, Alan Fields Institute 01-Jul-13 30-Dec-13 Tseng, Hsian-Hua Ohio State University 14-Oct-13 20-Oct-13 van Garrel, Michel Fields Institute 01-Jul-13 31-Dec-13 Yui, Noriko Queen's University 02-Jul-13 20-Dec-13 Zaslow, Eric Northwestern University 17-Oct-13 20-Oct-13 Zhang, Zheng Stony Brook University 15-Oct-13 19-Oct-13 Zhu, Yuecheng University of Texas at Austin 01-Jul-13 23-Nov-13 Zinger, Aleksey Stony Brook University 17-Oct-13 20-Oct-13