Monday, May 12 at 1:00pm: Geometry and Topology Seminar - Alvaro Pelayo

Geometry and Topology Seminar
4-manifolds with torus actions
Alvaro Pelayo, MIT

After reviewing the definition of symplectic manifold, symplectic action and some basic results on Hamiltonian torus actions, I will present a classification of symplectic actions of tori on (compact, connected) four-manifolds. The classification is in terms of a collection of invariants of the topology of the manifold, of the torus action and of the symplectic form. I will present explicit models of such symplectic manifolds with torus actions, defined in terms of these invariants. A stepping stone for this classification is the previous classification of symplectic torus actions with coisotropic principal orbits due to JJ Duistermaat and the speaker.

1:00pm-2:15pm, Monday, May 12, 2008 in LGRT 1535

Tuesday, May 13 at 4:00pm: Applied Mathematics and Computation Seminar - Timo Seppalainen

Applied Mathematics and Computation Seminar
Fluctuation results for some models of random environments and interactions
Timo Seppalainen, University of Wisconsin

This talk is a survey of some recent fluctuation results for three stochastic models: ballistic random walk in random environment, the random average process, and the asymmetric simple exclusion process. We will see fluctuations of different magnitudes, expressed as powers of the ratio between macroscopic and microscopic space and time scales.

Refreshments at 3:45

4:00pm-5:00pm, Tuesday, May 13, 2008 in LGRT 1634

UMass Amherst Math/Stat Seminars (Weekly Schedule)

Monday, May 12 at 1:00pm: Geometry and Topology Seminar - Alvaro Pelayo

Tuesday, May 13 at 4:00pm: Applied Mathematics and Computation Seminar - Timo Seppalainen