The seminar takes place on Thursdays 3:30 pm - 4:30 pm in room 2-449.
Please contact Shaoyun (shaoyunb@mit.edu) for seminar-related matters.
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Organizers: Shaoyun Bai and Paul Seidel.
| Date | Speaker | Title and Abstract |
|---|---|---|
| Feb 20 |
Juan Muñoz-Echániz (SCGP) | Boundary Dehn twists on symplectic 4-manifolds with Seifert-fibered boundary
Show/hide abstractIn this talk I will discuss the following result: the boundary Dehn twist on a symplectic filling M of a Seifert-fibered rational homology 3-sphere (negatively-oriented, equipped with its canonical contact structure) has infinite order in the smooth mapping class group of M (fixing the boundary) provided b^+ (M) > 0. This result has applications to the monodromy of surface singularities, such as: the monodromy diffeomorphism of a weighted-homogeneous isolated hypersurface singularity of complex dimension 2 has infinite order in the smooth mapping class group of its Milnor fiber, provided the singularity is not ADE. (In turn, the ADE singularities have finite order monodromy by Brieskorn’s Simultaneous Resolution Theorem.)The proof involves studying the Seiberg—Witten equation in 1-parametric families of 4-manifolds, by a combination of techniques from Floer homology, symplectic and contact geometry. I will also explain how to use our techniques to obstruct boundary Dehn twists from factorising as products of Seidel—Dehn twists on Lagrangian 2-spheres and/or their squares, in both the smooth and/or symplectic mapping class groups. This is based on joint work with Hokuto Konno, Jianfeng Lin and Anubhav Mukherjee. |
| Feb 27 |
Ju Tan (Boston University) | Deformation spaces of Lagrangian immersions and quiver varieties
Show/hide abstractQuiver possesses a rich representation theory, deeply connected to instantons and coherent sheaves as illuminated by the ADHM construction and the works of many others. Besides, quivers also capture the formal deformation space of a Lagrangian submanifold. In this talk, we will discuss these relations from the perspective of SYZ mirror symmetry. In particular, we will introduce the framed Lagrangian immersions, the Maurer-Cartan deformation spaces of which are Nakajima quiver varieties. If time permits, we will discuss our ongoing projects on the Hecke correspondence and Nakajima's raising operators. This is based on the joint work with Jiawei Hu and Siu-Cheong Lau, and an ongoing project with Siu-Cheong Lau. |
| Mar 6 |
Charles Doran (Alberta) | Fibration and Degeneration in Calabi-Yau Geometry
Show/hide abstractAt String-Math 2015 in Sanya, I gave evidence for a new geometric duality that conjecturally connects mirror pairs of Calabi-Yau manifolds with extra structure: fibrations on one side and degenerations on the other. The “DHT mirror symmetry” conjecture unifies mirror constructions for the Calabi-Yau and Fano/Landau-Ginzburg cases. I will review the status of the DHT conjecture in several settings and describe proven implications in Hodge theory, geometry, and physics. |
| Mar 13 |
Andrew Hanlon (Dartmouth) | The Cox category and homological mirror symmetry
Show/hide abstractIn recent joint work with Ballard, Berkesch, Brown, Cranton Heller, Erman, Favero, Ganatra, and Huang, we introduced the Cox category of a toric variety in order to realize a modification of King's conjecture. I will explain how this construction relates to homological mirror symmetry and Fukaya categories. |
| Mar 20 |
Zihong Chen (MIT) | Singularity and decomposition of the quantum connection
Show/hide abstractThe (small) quantum connection is one of the simplest objects built out of Gromov-Witten invariants, yet it gives rise to a repertoire of rich and important questions. This connection has a simple pole (well-behaved) at infinity and a quadratic pole ay 0. Despite its simple form, very little is understood about the latter. In this talk, I will discuss my result that for all Fano symplectic manifolds, this quadratic singularity is of unramified exponential type—-meaning it has a "spectral decomposition" where each piece is as simple as possible. Surprisingly, the proof follows a reduction mod p argument, and uses Katz's classical monodromy theorem and the more recent quantum Steenrod operations in symplectic Gromov-Witten theory. If time permits, I will discuss other recent developments in the field regarding (p-adic) analytic decompositions of the quantum connection. |
| Apr 1 |
Noah Porcelli (Imperial College) in 2-361 , 3pm - 4pm | Parametrised Whitehead torsion of families of nearby Lagrangians
Show/hide abstractThe parametrised Whitehead torsion is an invariant of families of manifolds, and can be viewed as a map to an algebraic K-theory space. A strong version of the nearby Lagrangian conjecture says that when applied to families of closed exact Lagrangians in a cotangent bundle, this invariant vanishes. Abouzaid and Kragh showed that in this case, this map lands in the trivial path component of the target, i.e. is trivial on $\pi_0$. Using generating functions, we find strong constraints on what this map does to higher homotopy groups. I'll illustrate this with some concrete consequences for the symplectic mapping class group of $T^*T^n$ relative to the 0-section. This is based on joint work-in-progress with Sylvain Courte. |
| Apr 3 |
Shaowu Zhang (Caltech) | Spectral decomposition of nc-Hodge structures and F-bundles
Show/hide abstractNon-commutative Hodge structures were introduced by Katzarkov, Kontsevich, and Pantev as a generalization of classical Hodge structures for non-commutative spaces. Their formal (or non-archimedean) analogs are known as F-bundles. Such structures naturally appear in mirror symmetry, enumerative geometry, and singularity theory. In this talk, I will first discuss the spectral decomposition of nc-Hodge structures of exponential type and relate it to the vanishing cycle decomposition after Fourier transforms via certain choices of Gabrielov paths. I will then discuss the spectral decomposition of maximal F-bundles. If time permits, I will also talk about the extension of framings for F-bundles and its applications. This talk is based on joint works with T. Yu, T. Hinaul, and C. Zhang. |
| Apr 10 |
Jonathan Zung (MIT) | Pseudo-Anosov flows and stable Hamiltonian structures
Show/hide abstractThe Nielsen-Thurston classification gives a canonical representative of a mapping class group of a surface. Recent progress in pseudo-Anosov dynamics allows us to prove analogous statements for flows on 3-manifolds: a pseudo-Anosov flow is a canonical representative of its underlying stable Hamiltonian structure. I'll survey some applications to finiteness problems in Dehn surgery. |
| Apr 17 |
Egor Shelukhin (Montreal) | Non-orderability and the contact Hofer metric
Show/hide abstractWe discuss a recent joint work with Jakob Hedicke which relates contact non-orderability, the existence of positive contractible loops in the contactomoprhism group, and shortening in the contact Hofer metric. Together with considerations of contact open books, this shows that contact boundaries one-stabilizations of Weinstein manifolds, including the standard tight S^1 x S^2, are non-orderable. |
| Apr 24 |
Dun Tang (Berkeley) | A Dijkgraff-Witten type reconstruction formula for g=1 quantum K-invariants
Show/hide abstractQuantum K-invariants are defined as holomorphic Euler characteristics on the moduli space of stable maps, incorporating products of universal cotangent bundles and virtual bundles pulled back from the target space. These invariants enumerate the dimensions of sheaf cohomology. In this talk, I will present a reconstruction formula for general genus-one quantum K-invariants, expressing them in terms of genus-zero invariants and genus-one invariants with at most one marked point carrying a universal cotangent line bundle. |
| May 1 |
Filip Živanovic (SCGP) | Equivariant Floer theory for symplectic C*-manifolds
Show/hide abstractI will talk about a series of joint papers with Alexander Ritter, where we examine a large class of non-compact symplectic manifolds, including semiprojective toric varieties, conical symplectic resolutions, Higgs moduli spaces, etc. These manifolds admit a Hamiltonian circle action which is part of a pseudo-holomorphic C*-action. The symplectic form on these spaces is typically non-exact at infinity, yet we can make sense of Hamiltonian Floer cohomology for functions of the moment map of the circle action. We showed that these Floer cohomologies induce filtration by ideals on quantum cohomology, computable using certain Morse-Bott-Floer spectral sequences. I will explain recent progress on equivariant Floer cohomology for these spaces, in which case we obtain a filtration on equivariant quantum cohomology. |
| May 8 |
Johan Asplund (Stony Brook) | TBA
Show/hide abstract |
| Date | Speaker | Title and Abstract |
|---|---|---|
| Sep 12 |
Sebastian Haney (Columbia) | Open enumerative mirror symmetry for lines in the mirror quintic
Show/hide abstractOne of the early achievements of mirror symmetry was the prediction of genus zero Gromov-Witten invariants for the quintic threefold in terms of period integrals on the mirror. Analogous predictions for open Gromov-Witten invariants in closed Calabi-Yau threefolds can be formulated in terms of relative period integrals on the mirror, which govern extensions of variations of Hodge structure. I will discuss work in preparation in which I construct an immersed Lagrangian in the quintic and show that it supports a family of objects in the Fukaya category mirror to vector bundles on lines in the mirror quintic. The open Gromov-Witten invariants of this Lagrangian are irrational, and can be computed from homological mirror symmetry. |
| Sep 19 | Yunpeng Niu (Stony Brook) |
A Monoidal Structure on the Fukaya Category
Show/hide abstractHomological mirror symmetry suggests that there should exist on the Fukaya category certain structures analogous to those known on the derived category of coherent sheaves. In 2010, A. Subotic associated a natural monoidal structure on the generalized Donaldson-Fukaya category, mirror to the tensor product of coherent sheaves, when the symplectic manifold is equipped with a smooth Lagrangian fibration with a distinguished Lagrangian section. In this talk, I will describe a generalization of this result: how given a Lagrangian fibration (with section) with focus-focus type singularities on a symplectic 4-fold M, one can associate a natural immersed Lagrangian correspondence from M \times M to M. In the case of a generic elliptic K3, I will explain why such a correspondence is unobstructed and how it induces a monoidal structure on the Fukaya category of M. This is part of joint work with M. Abouzaid and N. Bottman. |
| Sep 26 | Guangbo Xu (Rutgers) | Quantum Kirwan map and quantum Steenrod operation
Show/hide abstractGiven a symplectic manifold with a Hamiltonian -action, the classical Kirwan map from the equivariant cohomology to the cohomology of the symplectic reduction preserves the multiplicative structure. If we consider the equivariant quantum cohomology and the quantum cohomology of the reduction space, both defined via counting holomorphic spheres, then Salamon conjectured that a quantum deformation of the Kirwan map can be defined by counting certain gauge-theoretic objects (affine vortices). I will explain my recent proof of this conjecture under certain monotonicity condition. Moreover, if we further extend the quantum Kirwan map -equivariantly, then one can define a map which intertwines the classical Steenrod operations on classifying spaces and the quantum Steenrod operation (defined by Seidel-Wilkins) on the symplectic reduction. |
| Oct 3 | Semon Rezchikov (Princeton) | Cyclotomic Structure In Symplectic Topology
Show/hide abstractSymplectic cohomology is a fundamental invariant of a symplectic manifold M with contact type boundary that is defined in terms of dynamical information and counts of pseudoholomorphic genus zero curves, and carries algebraic structures that parallel the algebraic structures on the Hochschild (co)homology of the Fukaya category of M. We show, under natural topological assumptions, that the symplectic cohomology is the homology of a genuine p-cyclotomic spectrum in the sense of Nikolaus-Scholze. The cyclotomic structure arises geometrically from the map which sends loops in M to their p-fold iterates. The data of this refinement is expected to produce many new algebraic structures of an arithmetic nature on symplectic cohomology, analogously to the way that prismatic cohomology refines the de Rham cohomology of a variety. The talk will explain the result and, if time permits, discuss concrete connections to equivariant string topology, to equivariant Floer homology operations, and to arithmetic geometry. |
| Oct 17 | Keeley Hoek (Harvard) | Family Floer theory via Morse theoretic technology
Show/hide abstractThe family Floer program gives a modern reinterpretation of the construction of the mirror of an SYZ fibration \pi : X \to B, namely as a moduli space of objects of the Fukaya category of X supported on the fibers of the fibration. The resulting rigid analytic mirror \check{X} comes equipped with a functor from the Fukaya category of X into coherent sheaves on \check{X} which can then, as an application, be used to try to prove homological mirror symmetry. In this talk I will discuss a new Morse theoretic model of family Floer theory via pseudoholomorphic treed disks, extending ideas of Charest--Woodward and Auroux. |
| Oct 22 | Nick Sheridan (Edinburgh), in 2-361 , 4pm - 5pm | Homological mirror symmetry for Calabi-Yau hypersurfaces in toric varieties
Show/hide abstractKontsevich's homological mirror symmetry conjecture predicts an equivalence between the derived category of coherent sheaves on one algebraic variety X, and the Fukaya category of a 'mirror' symplectic manifold Y. A broad class of conjectural mirror pairs (X,Y) of Calabi-Yau hypersurfaces in toric varieties was constructed by Batyrev. We prove Kontsevich's conjecture for a large subset of such Batyrev mirror pairs, in all but finitely many characteristics. The key ingredients are Gammage-Shende's proof of homological mirror symmetry 'at large volume' (which uses Ganatra-Pardon-Shende's work to reduce the computation of the Fukaya category to microlocal sheaf theory), and a deformation argument to a neighbourhood of the large volume limit using Seidel's relative Fukaya category. Based on joint work with Sheel Ganatra, Andrew Hanlon, Jeff Hicks, and Dan Pomerleano. |
| Oct 31 | Kai Hugtenburg (Lancaster) | Open Gromov-Witten invariants and Mirror symmetry
Show/hide abstractThis talk reports on two projects. The first work (in progress), joint with Amanda Hirschi, constructs (genus 0) open Gromov-Witten invariants for any Lagrangian submanifold using a global Kuranishi chart construction. As an application we show open Gromov-Witten invariants are invariant under Lagrangian cobordisms. I will then describe how open Gromov-Witten invariants fit into mirror symmetry, which brings me to the second project: obtaining open Gromov-Witten invariants from the Fukaya category. |
| Nov 7 | Yash Deshmukh (IAS) | Plumber’s algebra structure on symplectic cohomology
Show/hide abstractI will introduce a new structure on (relative) symplectic cohomology defined in terms of a PROP called the “Plumber’s PROP.” This PROP consists of nodal Riemann surfaces, of all genera and with multiple inputs and outputs, satisfying a condition that ensures the existence of positive Floer data on the surfaces. This action is defined on the chain-level and generalizes the work of Abouzaid–Groman–Varolgunes. I will discuss the relationship of this structure to cohomological field theories, with potential applications to curve counts, as well as algebraic structures defined on variants of symplectic cohomology such as Rabinowitz Floer cohomology. |
| Nov 14 | Lea Kenigsberg (UC Davis) | The string topology coproduct and why it is so cool
Show/hide abstractLet $M$ be a smooth manifold, for example a higher dimensional sphere. The free loop space is the space of all maps from the circle to $M$. Theloop space admits a very rich structure which reveals geometric andtopological information about manifoldsIn this talk I will describe the string topology coproduct, and the kind of information it encodes. In particular, I will discuss connections to invariants from Algebraic $K$ theory and Fixed point theory. This is based on joint work with Noah Porcelli. |
| Nov 21 | Joshua Greene (Boston College) | Symplectic geometry and inscription problems
Show/hide abstractThe square peg problem was posed by Otto Toeplitz in 1911. It asks whether every Jordan curve in the place contains the vertices of a square, and it is still open to this day. I will survey the approaches to this problem and its relatives using symplectic geometry. This talk is based on joint work with Andrew Lobb. |
| Dec 4 | Eric Kilgore (Stanford), in 2-361 , 12 - 1pm | Legendrian non-squeezing via microsheaves
Show/hide abstractIn this talk I will explain some quantitative embedding results for Legendrian submanifolds of pre-quantization spaces. To start, I will recall some contact non-squeezing results for domains, and present an elementary proof of Legendrian non-squeezing for lifts of integral Lagrangian loops in T*R, using some variations on normal rulings. Then I will explain how to generalize this to high dimensions using the language of microsheaves. If time permits, as an application, I will show that the Legendrian lifts of certain monotone Lagrangian tori in \mathbb{C}^n are not squeezable. |
| Dec 5 | Jie Min (UMass Amherst), in 2-361 | Symplectic log Calabi-Yau divisors and almost toric fibrations
Show/hide abstractLagrangian fibrations sit at the crossroads of integrable systems, toric symplectic geometry and mirror symmetry. A particularly simple and interesting class of Lagrangian fibrations is called almost toric fibrations, whose total spaces are symplectic 4-manifolds. In this talk I will introduce almost toric fibrations over disks and their boundary preimages, which are symplectic divisors representing the first Chern class, called symplectic log Calabi-Yau divisors. I will then talk about joint work with Tian-Jun Li and Shengzhen Ning, showing that given a symplectic log Calabi-Yau divisor, an almost toric fibration can be constructed. |