## Seminars and Colloquia by Series

Friday, February 26, 2010 - 14:00 , Location: Skiles 269 , Qi Chen , Winston-Salem State University , Organizer: Thang Le
For every quantum group one can define two invariants of 3-manifolds:the WRT invariant and the Hennings invariant. We will show that theseinvariants are equivalentfor quantum sl_2 when restricted to the rational homology 3-spheres.This relation can be used to solve the integrality problem of the WRT invariant.We will also show that the Hennings invariant produces integral TQFTsin a more natural way than the WRT invariant.
Sunday, January 10, 2010 - 15:00 , Location: TBA , Matt Clay , Allegheny College , Organizer: Dan Margalit
Monday, November 30, 2009 - 14:05 , Location: Skiles 269 , , Georgia Tech , , Organizer: Stavros Garoufalidis
I will discuss a conjecture that relates the degree of the Jones polynomial of a knot and its parallels with the slopes of incompressible surfaces in the knot complement. I will present examples, as well as computational challenges.
Monday, November 23, 2009 - 14:00 , Location: Skiles 269 , , Mathematical Institute of Academy of Sciences of the Czech Republic , Organizer: Thang Le
In 1979 Valiant gave algebraic analogs to algorithmic complexity problem such as $P \not = NP$. His central conjecture concerns the determinantal complexity of the permanents. In my lecture I shall propose geometric and algebraic methods to attack this problem and other lower bound problems based on the elusive functions approach by Raz. In particular I shall give new algorithms to get lower bounds for determinantal complexity of polynomials over $Q$, $R$ and $C$.
Monday, November 9, 2009 - 14:00 , Location: Skiles 269 , Bulent Tosun , Ga Tech , Organizer: John Etnyre
In 3-dimensional  contact topology one of the main problem  is classifying Legendrian (transverse) knots in certain knot type up to Legendrian ( transverse) isotopy. In particular we want to decide if two (one in case of transverse knots) classical invariants of this knots are complete set of invariants. If it is, then we call this knot type Legendrian (transversely) simple knot type otherwise it is called Legendrian (transversely)  non-simple. In this talk, by tracing the techniques developed by Etnyre and Honda, we will present some  results  concerning  the complete Legendrian and transverse classification of certain cabled knots in the  standard tight contact 3-sphere. Moreover we will provide an infinite family of  Legendrian  and  transversely non-simple prime knots.
Wednesday, October 28, 2009 - 15:00 , Location: Skiles 255 , , University of Amsterdam , , Organizer: Stavros Garoufalidis
We recall the Schur Weyl duality from representation theory and show how this can be applied to express the colored Jones polynomial of torus knots in an elegant way. We'll then discuss some applications and further extensions of this method.
Monday, October 26, 2009 - 14:00 , Location: Skiles 269 , Shea Vela-Vick , Columbia University , Organizer: John Etnyre
To each three-component link in the 3-dimensional sphere we associate a characteristic map from the 3-torus to the 2-sphere, and establish a correspondence between the pairwise and Milnor triple linking numbers of the link and the Pontryagin invariants that classify its characteristic map up to homotopy. This can be viewed as a natural extension of the familiar fact that the linking number of a two-component link is the degree of its associated Gauss map from the 2-torus to the 2-sphere.In the case where the pairwise linking numbers are all zero, I will present an integral formula for the triple linking number analogous to the Gauss integral for the pairwise linking numbers. The integrand in this formula is geometrically natural in the sense that it is invariant under orientation-preserving rigid motions of the 3-sphere.
Monday, October 19, 2009 - 14:00 , Location: Skiles 269 , Inanc Baykur , Brandeis University , Organizer: John Etnyre
We will introduce new constructions of infinite families of smooth structures on small 4-manifolds and infinite families of smooth knottings of surfaces.
Monday, October 12, 2009 - 14:05 , Location: Skiles 269 , , UTexas Austin , , Organizer: Stavros Garoufalidis
The deformation variety is similar to the representation variety inthat it describes (generally incomplete) hyperbolic structures on3-manifolds with torus boundary components. However, the deformationvariety depends crucially on a triangulation of the manifold: theremay be entire components of the representation variety which can beobtained from the deformation variety with one triangulation but notanother, and it is unclear how to choose a "good" triangulation thatavoids these problems. I will describe the "extended deformationvariety", which deals with many situations that the deformationvariety cannot. In particular, given a manifold which admits someideal triangulation we can construct a triangulation such that we canrecover any irreducible representation (with some trivial exceptions)from the associated extended deformation variety.
Monday, October 5, 2009 - 14:00 , Location: - , - , - , Organizer: John Etnyre