Symplectic Geometry Seminar

Wednesday 3:30pm-4:30pm VV B139

• If you would like to talk in the seminar but have difficulty with adding information here, please contact Dongning Wang

date	speaker	title	host(s)
Sept. 21st	Ruifang Song	The Picard-Fuchs equations of Calabi-Yau hypersurfaces in partial flag varieties
Sept. 28st	Ruifang Song	The Picard-Fuchs equations of Calabi-Yau hypersurfaces in partial flag varieties(continued)
Oct. 5th	Dongning Wang	Seidel Representation for Symplectic Orbifolds
Oct. 12th	Dongning Wang	Seidel Representation for Symplectic Orbifolds(continued)
Oct. 26th	Jie Zhao	Mirror Symmetry and Quantum Correction
Nov. 23th	Jaeho Lee	Tropical curves and Toric varieties(continued)

Abstracts

Ruifang Song The Picard-Fuchs equations of Calabi-Yau hypersurfaces in partial flag varieties

Abstract

We introduce a system of differential equations associated to a smooth algebraic variety X acted by a complex Lie group G and a G-linearlized line bundle L on X. We show that this system is holonomic and thus has finite dimensional solution space assuming G acts on X with finitely many orbits. When X is a partial flag variety, we show that this system gives the Picard-Fuchs system of Calabi-Yau hypersurfaces in X. In particular, when X is a toric variety, our construction recovers GKZ systems and extended GKZ systems, which have played important roles in studying periods of Calabi-Yau hypersurfaces/complete intersections in toric varieties. In general, if X is a Fano variety, L is the anticanonical line bundle and G=Aut(X), this construction can be used to study the Picard-Fuchs system of Calabi-Yau hypersurfaces/complete intersections in X.

Dongning Wang Seidel Representation for Symplectic Orbifolds

For a symplectic manifold [math]\displaystyle{ (M,\omega) }[/math], Seidel representation is a group morphism from [math]\displaystyle{ \pi_1(Ham(M,\omega)) }[/math] to the multiplication group of the quantum cohomology ring [math]\displaystyle{ QH^*(M,\omega) }[/math]. With this morphism, once given enough information about [math]\displaystyle{ \pi_1(Ham(M,\omega)) }[/math], one can get compute [math]\displaystyle{ QH^*(M,\omega) }[/math]. On the other side, one would like to compute quantum cohomology of symplectic orbifolds defined by Chen and Ruan for many reasons, for example, to verify mirror symmetry between orbifolds and its mirror. With this motivation, we generalize Seidel representation to the orbifold cases. To do that, we need to generalize all the terminologies used to construct Seidel representation. For a symplectic orbifold [math]\displaystyle{ (\mathcal{X},\omega) }[/math], we define loops of Hamiltonian diffeomorphisms, [math]\displaystyle{ \pi_1(Ham(\mathcal{X},\omega)) }[/math], Hamiltonian orbifiber bundles, and sectional pseudoholomorphic orbicurves into the bundle. In this talk, I will explain these definitions and use them to construct Seidel representation for orbifolds. This is a joint work with Hsian-Hua Tseng.

Past Semesters

• Spring 2011 Symplectic Geometry Seminar