The SGGTC seminar meets on Fridays in Math 407 at 1pm, unless noted otherwise (in red).

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 Date Speaker Title Jan. 20 Wai-kit Yeung (Cornell University) Perverse sheaves, knot contact homology and relative Calabi-Yau completions Jan. 27-29 FRG Workshop: Crossing the Walls in Enumerative Geometry Feb. 3 Daniel Tubbenhauer (University of Bonn) Representation theory of Coxeter groups:Some first steps Feb. 10 Pavel Mnev (University of Notre Dame) Abelian and non-abelian BF theory on cobordisms endowed with cellular decomposition Feb. 17 Ina Petkova (Dartmouth College) Tangle Floer homology and quantum gl(1|1) Feb. 24 Bohan Fang (Peking University) Oscillatory integrals on the T-dual cycles Mar. 3 Tye Lidman (NCSU) Concordance in homology spheres Mar. 10 Alexandru Oancea ( IAS/Institut de Mathématiques de Jussieu) TBA Mar. 13-17 Workshop on Homological Mirror Symmetry: Emerging Developments and Applications (IAS) Mar. 24 Weiwei Wu (University of Georgia) Mar. 31 Ran Tessler TBA Apr. 7 10:30am Math 520 Hiro Lee Tanaka (Harvard University) TBA Apr. 7 Aliakbar Daemi (SCGP) TBA Apr. 14 Apr. 21 Stephan Wehrli (Syracuse University) TBA Apr. 28 Lino Amorim (Boston University) TBA

# Abstracts

#### January 20, 2017: Wai-kit Yeung " Perverse sheaves, knot contact homology and relative Calabi-Yau completions"

Abstract: In this talk, I will present joint work [arXiv:1610.02438] with Yu. Berest and A. Eshmatov, where we give a universal construction, called homotopy braid closure, that produces invariants of links in R^3 starting with a braid group action on objects of a (model) category. Applying this construction to the natural action of the braid group B_n on the category of perverse sheaves on the two-dimensional disk with singularities at n marked points, we obtain a differential graded (DG) category that gives knot contact homology in the sense of L. Ng. As an application, we show that the category of finite-dimensional modules over the 0-th homology of this DG category is equivalent to the category of perverse sheaves on R^3 with singularities at most along the link. If time allows, I will also discuss my recent work [arXiv:1612.06352] that generalizes this picture using non-commutative algebraic geometry.

#### February 3, 2017: Daniel Tubbenhauer " Representation theory of Coxeter groups:Some first steps"

Abstract: This talk is an introduction as well as a survey about 2-representation theory of Coxeter groups. The motivation to study such 'higher' representations is as follows: In groundbreaking work Chuang-Rouquier and, independently, Khovanov-Lauda introduced 2-representation theory of Lie algebras and their quantum analogs. As a 'higher' version of classical representation theory of Lie groups, their ideas have already led to many successive works as well as applications throughout mathematics (and physics). Historically speaking, what should have come first' is 2-representation theory of finite groups. Sadly the story of higher' representations of finite groups is not understood at all at the moment. But, quite recently, Mazorchuk-Miemietz made very good progress towards a 'higher' analog of representations of finite-dimensional algebras (as e.g. groups rings of finite groups), and applied it quite successful to one of the most well-behaved family of finite groups: finite Coxeter groups. Already in this case a lot of interesting new phenomena show up, most of which are neither present in classical representation theory nor in the story of Chuang-Rouquier, Khovanov-Lauda, and which might lead to interesting connections and applications in the years to come. However, in this talk we will focus on one (completely explicit) example, i.e. the first non-trivial family of examples given by the dihedral groups, where already several new phenomena are visible. Based on joint work with Marco Mackaay, Volodymyr Mazorchuk and Vanessa Miemiet.

#### February 10, 2017: Pavel Mnev " Abelian and non-abelian BF theory on cobordisms endowed with cellular decomposition"

Abstract: We will present an example of a topological field theory living on cobordisms endowed with CW decomposition (this example corresponds to the so-called BF theory in its abelian and non-abelian variants), which satisfies the Batalin-Vilkovisky master equation, satisfies (a version of) Segal's gluing axiom w.r.t. concatenation of cobordisms and is compatible with cellular aggregations. In non-abelian case, the action functional of the theory is constructed out of local unimodular L-infinity algebras on cells; the partition function carries the information about the Reidemeister torsion, together with certain information pertaining to formal geometry of the moduli space of local systems. This theory provides an example of the BV-BFV programme for quantization of field theories on manifolds with boundary in cohomological formalism. This is a joint work with Alberto S. Cattaneo and Nicolai Reshetikhin.

#### February 17, 2017: Ina Petkova " Tangle Floer homology and quantum gl(1|1) "

Abstract: The Reshetikhin-Turaev construction for the standard representation of the quantum group gl(1|1) sends tangles to C(q)-linear maps in such a way that a knot is sent to its Alexander polynomial. After a brief review of this construction, I will give an introduction to tangle Floer homology — a combinatorial generalization of knot Floer homology which sends tangles to (homotopy equivalence classes of) bigraded dg bimodules. Finally, I will discuss how to see tangle Floer homology as a categorification of the Reshetikhin-Turaev invariant. This is joint work with Alexander Ellis and Vera Vertesi.

#### February 24, 2017: Bohan Fang " Oscillatory integrals on the T-dual cycles "

Abstract: The mirror of a complete toric variety is a Landau-Ginzburg model. The oscillatory integral of the superpotential function on a Lagrangian cycle mirror to a coherent sheaf is a B-model genus 0 invariant. I will describe a way to compute it, and it is mirror to a genus 0 Gromov-Witten descendant potential with certain Gamma class of the coherent sheaf inserted. This result is related to Iritani's result identifying the integral structures on both sides. When the toric variety is P^1, this result can be extended to compute all genus descendants from Eynard-Orantin's topological recursion theory on the mirror of P^1.

#### March 3, 2017: Tye Lidman " Concordance in homology spheres "

Abstract: Although not every knot in the three-sphere can bound a smooth embedded disk in the three-sphere, it must bound a PL disk in the four-ball. This is not true for knots in the boundaries of arbitrary smooth contractible manifolds. We give new examples of knots in homology spheres that cannot bound PL disks in any bounding homology ball and thus not concordant to knots in the three-sphere. This is joint work with Jen Hom and Adam Levine.

## Our e-mail list.

Announcements for this seminar, as well as for related seminars and events, are sent to the "Floer Homology" e-mail list maintained via Google Groups.