Georgia Institute of Technology College of Sciences

Contact geometry in three dimensions is a land of two disjoint classes ofcontact structures; overtwisted vs. tight. The former ones are flexible,means their geometry is determined by algebraic topology of underlying twoplane fields. In particular their existence and classification areunderstood completely. Tight contact structure, on the other hand, arerigid. The existence problem of a tight contact structure on a fixed threemanifold is hard and still widely open. The classification problem is evenharder.

In this talk we will extend the sutured product disk decompositions from the last talk to construct foliations on some knot complements and see how this can help understand the minimal genus of Seifert surfaces for knots and links.

Gabai has a nice criteria for recognizing fibered knots in 3-manifolds. This criteria is best described in terms of sutured manifolds and simple sutured hierarchies. We will introduce this terminology and prove Gabai's result. Given time (or in subsequent talks) we might discuss generalizations concerning constructing foliations on knot compliments and 3-manifolds in general. Such results are very useful in understanding the minimal genus representatives of homology classes in the manifold (in particular, the minimal genus of a Seifert surface for a knot).

The (blobbed) topological recursion is a recursive structure which defines, for any initial datagiven by symmetric holomorphic 1-form \phi_{0,1}(z) and 2-form \phi_{0,2}(z_1,z_2) (and symmetricn-forms \phi_{g,n} for n >=1 and g >=0), a sequence of symmetric meromorphic n-forms\omega_{g,n}(z_1,...,z_n) by a recursive formula on 2g - 2 + n.If we choose the initial data in various ways, \omega_{g,n} computes interesting quantities. A mainexample of application is that this topological recursion computes the asymptotic expansion ofhermitian matrix integrals.

No talk today. Ga Tech will be hosting a prospective graduate students day for undergraduates in the Georgia area.

We will discuss Milnor's classic proof of the existence of exotic smooth structures on the 7-sphere.

The $4$-genus of a knot is an important measure of complexity, related tothe unknotting number. A fundamental result used to study the $4$-genusand related invariants of homology classes is the Thom conjecture,proved by Kronheimer-Mrowka, and its symplectic extension due toOzsvath-Szabo, which say that closed symplectic surfacesminimize genus.Suppose (X, \omega) is a symplectic 4-manifold with contact type bounday and Sigma is a symplectic surface in X such that its boundary is a transverse knot in the boundary of X.