Georgia Institute of Technology College of Sciences

In this talk, I will present recent advancements in the study of smooth mapping class groups of 4-manifolds. Our work focuses on diffeomorphisms arising from Dehn twists along embedded 3-manifolds and their interaction with Seiberg-Witten theory. These investigations have led to intriguing applications across several areas, including symplectic geometry (related to Torelli symplectomorphisms), algebraic geometry (concerning the monodromy of singularities), and low-dimensional topology (involving exotic diffeomorphisms). This is collaborative work with Hokuto Konno, Jianfeng Lin, and Juan Munoz-Echaniz.

The Prym representations of the mapping class group are an important family of representations that come from abelian covers of a surface. They are defined on the level-ℓ mapping class group, which is a fundamental finite-index subgroup of the mapping class group.  One consequence of our work is that the Prym representations are infinitesimally rigid, i.e. they can not be deformed. We prove this infinitesimal rigidity by calculating the twisted cohomology of the level-ℓ mapping class group with coefficients in the Prym representation, and more generally in the r-tensor powers of the Prym representation. Our results also show that when r ≥ 2, this twisted cohomology does not satisfy cohomological stability, i.e. it depends on the genus g.

In this talk, we introduce contact invariants in bordered sutured Floer homology. Given a contact 3-manifold with convex boundary, we apply a result of Zarev to derive contact invariants in the bordered sutured modules BSA and BSD. We show that these invariants satisfy a pairing theorem, which is a bordered extension of the Honda-Kazez-Matic gluing map for sutured Floer homology. We also show that there is a correspondence between certain A-infinity operations in bordered modules and bypass attachment maps in sutured Floer homology. As an application, we characterize the Stipsicz-Vertesi map in terms of A-infinity action on CFA. If time permits, we will further discuss applications to contact surgery.