Seminars and Colloquia by Series

Monday, April 11, 2011 - 14:00 , Location: Skiles 006 , Nathan Geer , Utah State University , Organizer: John Etnyre
I will consider two constructions which lead to information about the topology of a 3-manifold from one of its triangulation.  The first construction is a modification of the Turaev-Viro invariant based on re-normalized 6j-symbols.  These re-normalized 6j-symbols satisfy tetrahedral symmetries.  The second construction is a generalization of Kashaev's invariant defined in his foundational paper where he first stated the volume conjecture.  This generalization is based on symmetrizing 6j-symbols using *charges* developed by W. Neumann, S. Baseilhac, and R. Benedetti.  In this talk, I will focus on the example of nilpotent representations of quantized sl(2) at a root of unity.  In this example, the two constructions are equal and give rise to a kind of Homotopy Quantum Field Theory.  This is joint work with R. Kashaev, B. Patureau and V. Turaev.
Monday, April 4, 2011 - 14:05 , Location: Skiles 006 , Thao Vuong , Georgia Tech , , Organizer: Stavros Garoufalidis
I will talk about some progress in proving the Degree Conjecture for torus knots. The conjecture states that the degree of a colored Jones polynomial colored by an irreducible representation of a simple Lie algebra g is locally a quadratic quasi-polynomial. This is joint work with Stavros Garoufalidis.
Monday, March 21, 2011 - 09:31 , Location: None , None , None , Organizer: John Etnyre
Monday, March 14, 2011 - 14:05 , Location: Skiles 006 , Bruce Solomon , Indiana University , , Organizer: Mohammad Ghomi
A smooth loop in 3-space is skew if it has no pair of parallel tangent lines. With M.~Ghomi, we proved some years ago that among surfaces with some positive Gauss curvature (i.e., local convexity) the absence of skewloops characterizes quadrics. The relationship between skewloops and negatively curved surfaces has proven harder to analyze, however. We report some recent progress on that problem, including evidence both for and against the possibility that the absence of skewloops characterizes quadricsamong surfaces with negative curvature.
Friday, March 11, 2011 - 14:00 , Location: Skiles 269 , Shea Vela-Vick , Columbia University , Organizer: John Etnyre
I plan to discuss a method for defining Heegaard Floer invariants for   3-manifolds.  The construction is inspired by contact geometry and has several interesting immediate applications to the study of tight contact structures on noncompact 3-manifolds.  In this talk, I'll focus on one basic examples and indicate how one defines a contact invariant which can be used to give an alternate proof of James Tripp's classification of tight, minimally twisting contact structures on the open solid torus. This is joint work with John B. Etnyre and Rumen Zarev.
Monday, February 28, 2011 - 14:05 , Location: Skiles 006 , Leah Childers , Pittsburg State U , Organizer: Dan Margalit
We will discuss the structure of the symmetric (or hyperelliptic) Torelli group. More specifically, we will investigatethe group generated by Dehn twists about symmetric separating curvesdenoted by H(S). We will show that Aut(H(S)) is isomorphic to the symmetricmapping class group up to the hyperelliptic involution. We will do this bylooking at the natural action of H(S) on the symmetric separating curvecomplex and by giving an algebraic characterization of Dehn twists aboutsymmetric separating curves.
Monday, February 21, 2011 - 14:00 , Location: Skiles 006 , Jeremy Van Horn-Morris , AIM , Organizer: John Etnyre
A theorem of Chris Wendl allows you to completely characterize symplectic fillings of certain open book decompositions by factorizations of their monodromy into Dehn twists.  Olga Plamenevskaya and I use this to generalize results of Eliashberg, McDuff and Lisca to classify the fillings of certain Lens spaces. I'll discuss this and a newer version of Wendl's theorem, joint with Wendl and Sam Lisi, this time for spinal open books, and discuss a few more applications.
Monday, February 14, 2011 - 14:00 , Location: Skiles 006 , Bulent Tosun , Ga Tech , Organizer: John Etnyre
In this talk we will exhibit many new phenomena in the structure of Legendrian and transverse knots by giving a complete classification of all cables of the positive torus knots. We will also provide two structural theorems to ensure when cable of a Legendrian simple knot type is also Legendrian simple. Part of the results are joint work with John Etnyre and Douglas LaFountain
Monday, February 7, 2011 - 15:05 , Location: Skiles 006 , Roland van der Veen , UCBerkeley , , Organizer: Stavros Garoufalidis
For knots the hyperbolic geometry of the complement is known to be relatedto itsJones polynomial in various ways. We propose to study this relationship morecloselyby extending the Jones polynomial to graphs. For a planar graph we will showhow itsJones polynomial then gives rise to the hyperbolic volume of the polyhedronwhose1-skeleton is the graph. Joint with Francois Gueritaud and FrancoisCostantino.
Monday, February 7, 2011 - 14:05 , Location: Skiles 006 , Dan Margalit , Georgia Tech , Organizer: Dan Margalit
The braid group embeds in the mapping class group, and so the symplectic representation of the mapping class group gives rise to a symplectic represenation of the braid group.  The basic question Tara Brendle and I are trying to answer is: how can we describe the kernel?  Hain and Morifuji have conjectured that the kernel is generated by Dehn twists.  I will present some progress/evidence towards this conjecture.