Joint IAS-PU Symplectic Geometry Seminar

Homological Mirror Symmetry for singularities of type $T_{pqr}$

Ailsa Keating
Columbia University
March 10, 2016
We present some homological mirror symmetry statements for the singularities of type $T_{p,q,r}$. Loosely, these are one level of complexity up from so-called 'simple' singularities, of types $A$, $D$ and $E$. We will consider some symplectic invariants of the real four-dimensional Milnor fibres of these singularities, and explain how they correspond to coherent sheaves on certain blow-ups of the projective space $\mathbb P^2$, as suggested notably by Gross-Hacking-Keel.

Subflexible symplectic manifolds

Kyler Siegel
Stanford University
March 3, 2016
After recalling some recent developments in symplectic flexibility, I will introduce a class of open symplectic manifolds, called "subflexible", which are not flexible but become so after attaching some Weinstein handles. For example, the standard symplectic ball has a Weinstein subdomain with nontrivial symplectic topology. These are exotic symplectic manifolds with vanishing symplectic cohomology.

Positive loops---on a question by Eliashberg-Polterovich and a contact systolic inequality

Peter Albers
Universität Münster
February 25, 2016
In 2000 Eliashberg-Polterovich introduced the concept of positivity in contact geometry. The notion of a positive loop of contactomorphisms is central. A question of Eliashberg-Polterovich is whether $C^0$-small positive loops exist. We give a negative answer to this question. Moreover we give sharp lower bounds for the size which, in turn, gives rise to a $L^\infty$-contact systolic inequality. This should be contrasted with a recent result by Abbondandolo et. al. that on the standard contact 3-sphere no $L^2$-contact systolic inequality exists.

Floer theory revisited

Mohammed Abouzaid
Columbia University
February 4, 2016
I will describe a formalism for (Lagrangian) Floer theory wherein the output is not a deformation of the cohomology ring, but of the Pontryagin algebra of based loops, or of the analogous algebra of based discs (with boundary on the Lagrangian). I will explain the consequences of quantum cohomology, and the expected applications of this theory.

Disc filling and connected sum

Kai Zehmisch
Universität Münster
February 27, 2015
In my talk I will report on recent work with Hansjörg Geiges about a strong connection between the topology of a contact manifold and the existence of contractible periodic Reeb orbits. Namely, if the contact manifold appears as non-trivial contact connected sum and has non-trivial fundamental group or torsion-free homology, then the existence is ensured. This generalizes a result of Helmut Hofer in dimension three.

The symplectic displacement energy

Peter Spaeth
GE Global Research
February 20, 2015
To begin we will recall Banyaga's Hofer-like metric on the group of symplectic diffeomorphisms, and explain its conjugation invariance up to a factor. From there we will prove the positivity of the symplectic displacement energy of open subsets in compact symplectic manifolds, and then present examples of subsets with finite symplectic displacement energy but infinite Hofer displacement energy. The talk is based on a joint project with Augustin Banyaga and David Hurtubise.

Symplectic homology via Gromov-Witten theory

Luis Diogo
Columbia University
February 13, 2015
Symplectic homology is a very useful tool in symplectic topology, but it can be hard to compute explicitly. We will describe a procedure for computing symplectic homology using counts of pseudo-holomorphic spheres. These counts can sometimes be performed using Gromov-Witten theory. This method is applicable to a class of manifolds that are obtained by removing, from a closed symplectic manifold, a symplectic hypersurface of codimension 2. This is joint work with Samuel Lisi.

Symplectic forms in algebraic geometry

Giulia Saccà
Member, School of Mathematics
January 30, 2015
Imposing the existence of a holomorphic symplectic form on a projective algebraic variety is a very strong condition. After describing various instances of this phenomenon (among which is the fact that so few examples are known!), I will focus on the specific topic of maps from projective varieties admitting a holomorphic symplectic form. Essentially, the only such maps are Lagrangian fibrations and birational contractions. I will motivate why one should care about these types of maps, and give many examples illustrating their rich geometry.