Everyone is welcome to attend. Refreshments will be served in the Math Lounge before the exam.

**Tuesday, April 30, 2013**

** BA 6183, 40 St. George Street**

** 2:00 p.m.**

**PhD Candidate**: Brent Pym

**PhD Advisor**: Marco Gualtieri

**PhD Thesis Title**: Poisson structures and Lie algebroids in complex geometry

http://www.math.toronto.edu/bpym/files/thesis/bpym-thesis-2013-04-26.pdf

**Abstract:**

This thesis is devoted to the study of holomorphic Poisson structures and Lie algebroids, and their relationship with differential equations, singularity theory and noncommutative algebra.

After reviewing and developing the basic theory of Lie algebroids in the framework of complex analytic and algebraic geometry, we focus on Lie algebroids over complex curves and their application to the study of meromorphic connections. We give concrete constructions of the corresponding Lie groupoids, using blowups and the Uniformization Theorem. These groupoids are complex surfaces that serve as the natural domains of definition for the fundamental solutions of ordinary differential equations with singularities. We explore the relationship between the convergent Taylor expansions of these fundamental solutions and the divergent asymptotic series that arise when one attempts to solve an ordinary differential equation at an irregular singular point.

We then turn our attention to Poisson geometry. After discussing the basic structure of Poisson brackets and Poisson modules on analytic spaces, we study the geometry of the degeneracy loci-where the dimension of the symplectic leaves drops. We explain that Poisson structures have natural residues along their degeneracy loci, analogous to the Poincaré residue of a meromorphic volume form. We discuss the local structure of degeneracy loci in small codimension, placing

a strong constraint on the singularities of the degeneracy hypersurfaces of generically symplectic Poisson structures. We use these results to give new evidence for a conjecture of Bondal.

Finally, we discuss the problem of quantization in noncommutative projective geometry. Using Cerveau and Lins Neto’s classification of degree-two foliations of projective space, we give normal forms for unimodular quadratic Poisson

structures in four dimensions, and describe the quantizations of these Poisson structures to noncommutative graded algebras. As a result, we obtain a (conjecturally complete) list of families of quantum deformations of projective three-space. Among these algebras is an “exceptional” one, associated with a twisted cubic curve. This algebra has a number of remarkable properties: for example, it supports a family of bimodules that serve as quantum analogues of the classical Schwarzenberger bundles.

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