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Séance du 5 février 2016

Lieu: IHP, salle 201** **

**11:00 ** Janko Latchev (Hamburg)
**Knot contact homology, string topology, and the cord algebra.**
*Abstract: *I will discuss recently completed joint work with K.Cieliebak, T.Ekholm
and L.Ng which provides a new proof of the isomorphism between (the
degree zero part of) Legendrian contact homology for the unit conormal bundle of a
smooth knot K in R^3 (known as knot contact homology) and the cord
algebra, a combinatorially defined invariant of such knots introduced in
work of L.Ng.

One of the important ingredients is a string topology version of the
cord algebra, which serves as an intermediary between the two objects we
ultimately want to relate..
**14:15 ** Gilberto Spano (Budapest)
**A categorification of the Alexander polynomial in ECH.**
*Abstract: *In 2010 Colin, Ghiggini, Honda and Hutchings defined a "hat" version of
an embedded contact homology ECK for knots in 3-manifolds. We will
describe this homology, a "full" version of ECK and also
generalizations to links with more then one component; we will then
prove that for any link L in a homology 3-sphere, the graded Euler
characteristic of ECK coincides with the (multivariable) Alexander
polynomial of L.
**16:00 ** Michael Khanevsky (Bruxelles)** **
**Lagrangian displacement energy and Hofer's norm of commutators.**
*Abstract:* Chekanov proved that the displacement energy of a Lagrangian L is
bounded from below by the minimal area of holomorphic spheres and disks
in (M;L). We discuss a similar bound by M. Usher for the energy needed to separate a pair of Lagrangian submanifolds in M. An application of this estimate shows that certain manifolds admit Hamiltonian commutators with large Hofer's norm..

Prochaine
séance: 1/04 (pas de séance en mars).
Autre activité symplectique à Paris: groupe de travail faisceaux.