# Jerusalem Mathematics Colloquium

Thursday, 22nd April 2004, 4:00 pm

Mathematics Building, Lecture Hall 2

##

Professor Bernhard Kroetz

(University of Oregon)

"Lagrangian submanifolds and moment convexity"

** Abstract: **
Let M be a compact connected symplectic manifold endowed with a
Hamiltonian torus action and associated momentum map $\Phi$.
The Atiyah-Guillemin-Sternberg convexity theorem asserts that
$\Phi(M)$ is a convex polyhedron.

For a Lagrangian submanifold Q of M we are interested in the image $\Phi(Q)$.
In this context Duistermaat extended the AGS-theorem and determined
a class of Lagrangians for which $\Phi(Q)=\Phi(M)$ holds.

The objective of this talk is to explain how one can further enlarge
Duistermaat's class of Lagrangians and still
preserve $\Phi(M)=\Phi(Q)$. One obtains useful applications
to classical eigenvalue problems and their Lie theoretic generalizations.
In particular we will explain how one can prove Kostant's non-linear
convexity theorem with symplectic methods.

We report on joint work with Michael Otto.

Light refreshments will be served in the faculty lounge at 3:30.

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