## Topology & Geometric Group Theory Seminar

## Fall 2011

### 1:30 – 2:30, Malott 203

### Tuesday, September 20

**Reyer
Sjamaar**, Cornell University

*(Almost) Lagrangian fibre bundles*

(Almost) Lagrangian fibre bundles arise from completely integrable
Hamiltonian systems. Such bundles have local normal forms
("action-angle variables") and have no local invariants. Two global
invariants, the monodromy and the Chern class, were identified by
Duistermaat. A refinement of the Chern class, now called the
Lagrangian class, was found by Dazord and Delzant. In this survey
talk I will define these invariants and show how they classify
(almost) Lagrangian fibre bundles.

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