Monday, June 16, 2014 - 14:00 , Location: Skiles 006 , Atreyee Bhattacharya , Indian Institute Of Science , Organizer: John Etnyre
In this talk we will discuss an ODE associated to the evolution of curvature along the Ricci flow. We talk about the stability of certain fixed points of this ODE (up to a suitable normalization). These fixed points include curvature of a large class of symmetric spaces.
Monday, May 5, 2014 - 14:05 , Location: Skiles 006 , Dan Margalit , Georgia Institute of Technology , Organizer: Dan Margalit
In joint work with Joan Birman and Bill Menasco, we describe a new finite set of geodesics connecting two given vertices of the curve complex. As an application, we give an effective algorithm for distance in the curve complex.
Monday, April 21, 2014 - 14:00 , Location: Skiles 006 , Faramarz Vafaee , MSU , Organizer: John Etnyre
Heegaard Floer theory consists of a set of invariants of three-and four-dimensional manifolds. Three-manifolds with the simplest HeegaardFloer invariants are called L-spaces and the name stems from the fact thatlens spaces are L-spaces. The primary focus of this talk will be on thequestion of which knots in the three-sphere admit L-space surgeries. Wewill also discuss about possible characterizations of L-spaces that do notreference Heegaard Floer homology.
Wednesday, April 16, 2014 - 14:00 , Location: Skiles 006 , Jeremy Van Horn-Morris , University of Arkansas , Organizer: John Etnyre
A monoidal subset of a group is any set which is closed under the product (and contains the identity). The standard example is Dehn^+, the set of maps whcih can be written as a product of right-handed Dehn twists. Using open book decompositions, many properties of contact 3-manifolds are encoded as monoidal subsets of the mapping class group. By a related construction, contact topology also produces a several monoidal subsets of the braid group. These generalize the notion of positive braids and Rudolphs ideas of quasipositive and strongly quasipositive. We'll discuss the construction of these monoids and some of the many open questions.
Monday, April 14, 2014 - 14:00 , Location: Skiles 006 , David Krcatovich , MSU , Organizer: John Etnyre
The set of knots up to a four-dimensional equivalence relation can be given the structure of a group, called the (smooth) knot concordance group. We will discuss how to compute concordance invariants using Heegaard Floer homology. We will then introduce the idea of a "reduced" knot Floer complex, see how it can be used to simplify computations, and give examples of how it can be helpful in distinguishing knots which are not concordant.
Friday, April 11, 2014 - 13:05 , Location: Skiles 006 , Christian Zickert , University of Maryland , firstname.lastname@example.org , Organizer: Stavros Garoufalidis
The Ptolemy coordinates are efficient coordinates for computingboundary-unipotent representations of a 3-manifold group in SL(2,C). Wedefine a slightly modified version which allows you to computerepresentations that are not necessarily boundary-unipotent. This givesrise to a new algorithm for computing the A-polynomial.
Monday, April 7, 2014 - 14:05 , Location: Skiles 006 , Xingru Zhang , SUNY Buffalo , Organizer: Thang Le
We show that each (p,q)-torus knot in the 3-sphere is determined by its A-polynomial and its knot Floer homology. This is joint work with Yi Ni.
Monday, March 31, 2014 - 14:05 , Location: Skiles 006 , Kevin Wortman , University of Utah , Organizer: Dan Margalit
Suppose that F is a field with p elements, and let G be the finite-index congruence subgroup of SL(n, F[t]) obtained as the kernel of the homomorphism that reduces entries in SL(n, F[t]) modulo the ideal (t). Then H^(n-1)(G;F) is infinitely generated. I'll explain the ideas behind the proof of the above result, which is a special case of a result that applies to any noncocompact arithmetic group defined over function fields.
Monday, March 10, 2014 - 14:05 , Location: Skiles 006 , Anh Tran , Ohio State University (Columbus) , Organizer: Thang Le
A non-trivial group G is called left-orderable if there exists a strict total ordering < on its elements such that g