January 15 |
Ismar Volic (Wellesley) |
Multivariable Calculus and Link Spaces |

January 22 |
Jongil Park (Seoul National U) |
Symplectic 4-manifolds with b_{2}^{+}=1 versus complex surfaces with p_{g}=0 |

January 29 |
Nick Kuhn (UVa) |
A new proof of a result of Arone and Mahowald
Crucial to Greg and Mark Mahowald's work on the homotopy groups of a d dimensional sphere, with d odd, is that certain spaces L(k,d) have mod 2 cohomology free over certain finite sub Hopf algebras of the Steenrod algebra. We show how formulae related to the Dickson invariants (Dickson, 1903) make it easy to reduce to the case when d = 1. If there is time, I may survey various proofs of the d=1 case, some of which involve the Steinberg module for the finite groups GL(k,F_2). |

February 5 |
Eric Finster (UVa) |
Simplicial Sets and the Calculus of Coends
Many common constructions of homotopy theory can be very succinctly described in the category of simplicial sets using the calculus of coends. I'll try to give a primer on the definition and use of coends and the survery some examples: skeletal filtrations, Postnikov towers, joins, and (ordinal) subdivision. |

February 12 |
Greg Arone (UVa) |
Operads, Modules, and the Chain Rule |

February 19 |
James Hughes (UVa) |
Operads: A Crash Course |

February 26 |
Nick Kuhn (UVA) |
Representing Homology with Manifolds |

March 5 |
No Seminar |
Spring Break |

March 12 |
Calder Wishne |
Topology and Robotics |

March 19 |
Victor Turchin (Kansas State University) |
Hodge Decomposition in the Homology of Long Knots
We will describe a natural splitting in the rational homology and homotopy of the spaces of long knots Emb(R1,R^N). This decomposition arises from the cabling maps in the same way as a natural decomposition in the homology of loop spaces arises from power maps. The generating function for the Euler characteristics of the terms of this splitting will be presented. Based on this generating function one can show that both the homology and homotopy ranks of the spaces in question grow at least exponentially. There are two more motivations to study this decomposition. First, it is related to the study of the homology of higher dimensional knots Emb(R^k,R^N). Second, it is deeply related to the question whether Vassiliev invariants can distinguish knots from their inverses. |

March 26 |
TBA |
TBA |

April 2 |
Joanna Kania-Bartoszynska (NSF) |
Topological applications of quantum invariants I will discuss several applications of quantum invariants of 3-manifolds derived form topological quantum field theories. Examples include criteria for periodicity of knots and manifolds, obstructions to embedding one manifold into another, and combinatorial formulas for computing integrals of simple closed curves over character variety of the surface against Goldman's symplectic measure. |

April 9 |
Mike Hill (UVA) |
Equivariant Homotopy Theory |

April 16 |
Ben Cooper (UCSD) |
Homology and 3-manifold cobordisms
I will describe recent work on topological field theory in three dimensions, explaining how an algebra yields a certain kind of 3-dimensional field theory in a functorial way, how this implies the existence of an action of certain 3-manifold cobordisms on the algebra's homology. |

April 23 |
Abdelmalek Abdesselam (UVA) |
Upper bounds for classical spin networks
In a recent article, Garoufalidis and van der Veen proposed an analogue of the volume conjecture for classical spin networks. These are generalizations of 3n-j coefficients from SU(2) recoupling theory for angular momentum in quantum mechanics. We will present new upper bounds on the evaluation of such networks, in the general case. For the case of drum graphs we also have lower bounds which allow for the exact determination of the growth rate when the number of `colors' goes to infinity. |

April 30 |
Jozef Przytycki (George Washington U) |
Algebra Situs: Panorama of Skein Modules
Skein Modules are algebraic object associated to a manifold, usually constructed as a formal linear combination of embedded (or immersed) submanifolds, or simplicial complexes, modulo locally defined relations. In more restricted setting skein module is a module associated to a 3-dimensional manifold, by considering linear combinations of links (or graphs) in the manifold, modulo properly chosen (skein) relations. It is the main object of the algebraic topology based on knots. In the choice of relations one takes into account several factors:
(i) Is the module we obtain accessible (computable)?
(ii) How precise are our modules in distinguishing 3-manifolds and links
in them?
(iii) Does the module reflect topology/geometry of a 3-manifold
(e.g. surfaces in a manifold, geometric decomposition of a manifold)?.
(iv) Does the module admit some additional structure (e.g.~filtration,
gradation, multiplication, Hopf algebra structure)?
In this talk we offer a panorama of skein modules. |