# Jerusalem Mathematics Colloquium

Thursday, 30th March 2006, 4:00 pm

Mathematics Building, Lecture Hall 2

#

Leonid Polterovich

(Tel Aviv University)

"Quasi-morphisms and quasi-states in symplectic topology"

## ** Abstract: **
A quasi-morphism of a group is "a homomorphism up to
a bounded error". This notion was introduced in the 80-ies
in connection with bounded cohomology theory (Gromov,
Brooks). It proved to be a useful tool in geometry, topology
and dynamics.

In the present talk I focus on quasi-morphisms on groups of
symplectic diffeomorphisms. They come from Floer theory --
the cornerstone of modern symplectic topology. I discuss a
link to the theory of quasi-states - a recently emerged
branch of functional analysis originated in quantum
mechanics.

The talk is based on joint works math.SG/0205247,
math.SG/0410338 with M.Entov and math.SG/0307011 with
P.Biran and M.Entov.

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

List of talks, 2005-06

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