Group actions on smooth 4manifolds
October 2526, 2013, University of Massachusetts, Amherst, MA
Organizing Committee
R. Inanc Baykur (University of Massachusetts), Weimin Chen (University of Massachusetts) and Daniel Ruberman (Brandeis University)
Speakers and participants


Goals
The aim of this 2day workshop is to bring together active researchers in group actions and smooth 4manifolds, ranging from leading experts to recent PhDs and graduate students, and provide a panorama of the field through a variety of talks and discussion sessions.
Registration and support
No registration is needed; if you are planning on attending the workshop, simply email any one of the organizers to let us know about it. We have reserved rooms for all the invited participants outside of Western Massachusetts at the UMass Hotel and Conference Center. This event is sponsored by University of Massachusetts funds (R. Inanc Baykur) and by the NSF FRG Grant DMS 1065784 and 1065827 as a part of the FRG Collaborative Research on "Topology and Invariants of Smooth 4Manifolds" (Weimin Chen and Daniel Ruberman).
Schedule
Friday, October 25 9:1510:15am TianJun Li 10:4511:45am Ian Hambleton 11:4512:15pm Discussion 12:15 2:00pm Lunch 2:00 3:00pm Nathan Sunukjian 3:30 4:30pm Weiwei Wu 4:30 5:00pm Tea 5:00 6:00pm Discussion 
Saturday, October 26 9:1510:15am Nima Anvari 10:4511:45am Daniel Herr 11:45 1:15pm Discussion 1:15 3:15pm Lunch 
All talks will be held at Room 1634 Lederle Graduate Research Tower, University of Massachusetts, Amherst. Friday group lunch will be at the University Club and tea will be at the lounge next to Room 1634. Directions to University of Massachusetts campus can be found here. Department of Mathematics and Statistics is located in the Lederle Graduate Research Tower (LGRT) which is a very short walking distance from the UMass Hotel. (UMass Campus map pdf)
Titles and abstracts of talks

Nima Anvari
Equivariant splitting of 4Manifolds
In this talk we consider free finite cyclic group actions on Seifert fibered homology spheres extending to smooth, homologically trivial actions on bounding, even negative definite 4manifolds. We obtain restrictions using equivariant YangMills gauge theory and as an application study smooth equivariant splittings of 4manifolds. 
Ian Hambleton
Smooth group actions on S^2 x S^2 and YangMills gauge theory
In the talk I will describe how certain constraints on smooth finite group actions on 4manifolds arise from studying an equivariant version of the YangMills moduli spaces. The main application is the conjecture that smooth actions of cyclic groups on S^2 x S^2 have standard rotation numbers. 
Daniel Herr
Open books on contact orbifolds
On 3manifolds, every open book supports a contact structure, and every contact structure is supported by an open book. This correspondence is due to Giroux, and is a major tool in the study of three dimensional contact geometry. I will discuss the extension of this result to the equivariant and orbifold categories. 
TianJun Li
Geometric automorphism group of symplectic 4manifolds
I will present some results about the homological action of the orientationpreserving diffeomorphism group of a symplectic 4manifold. (Joint work with Bo Dai and ChungI Ho). 
Nathan Sunukjian
Embedded surfaces and exotic group actions
It has long been known that exotic smooth structures on a 4manifold become the same after connect summing with enough copies of S^2 x S^2. There are two other notable kinds of exotic behavior observed in 4manifolds: exotic embeddings of surfaces, and exotic group actions. In this talk I'll explain the interrelations between these different kinds of exotic behaviors, and I'll describe an operation under which such exotic things again become smoothly equivalent. This work in progress is joint with Inanc Baykur. 
Weiwei Wu
Finite subgroups of symplectic Cremona group
Finite subgroup of Cremona group is a classical topic in algebraic geometry since the 19th century. In this talk we explain an extension of this problem to the symplectic category. In particular, we will explain the symplectic counterparts of two classical theorems. The first one due to Noether, says a plane Cremona map is decomposed into a sequence of quadratic transformations, which is generalized to the symplectic category on the homological level. The second one is due to Castelnuovo and Kantor, which says a minimal Gsurface either has a conic bundle structure or is a Del Pezzo surface. The latter theorem lies the ground of classifications of finite Cremona subgroups due to Dolgachev and Iskovskikh. This is an ongoing program joint with Weimin Chen and TianJun Li.