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Séance du 9 février 2018

Lieu: IHP, salle 01

**11:00 ** Marco Golla (Nantes)** **
**Obstructing planarity of contact 3-manifolds.*** *
*Abstract:* We give new obstructions to the existence of planar open
books for contact structures, in terms of the homology of their
fillings. I will talk about applications to links of surface
singularities, Seifert fibred spaces, and integral homology spheres.

This is joint work with Paolo Ghiggini and Olga Plamenevskaya..
** **
**14:15 **Jean-François Barraud (Toulouse)
**A Novikov fundamental group.**
*Abstract*: Morse theory explains how the topology of a manifold and the critical
points of smooth functions on this manifold are related. The Morse
homology and the associated Morse inequalities are a well known example,
but there might also be deeper constraints, that are homotopic in nature
and not detected by the homology.

SImilarly, the object of Novikov theory is to study how the topology of
the manifold and the "critical points" of Morse closed one forms are
related. Here also, there might be homotopical constraints that are not
detected by the Novikov homology. I will present an agebraic invariant
that captures some of this information, and is an analogue in Novikov
theory of the fundamental group in Morse theory. In particular, this
"Novikov fundamental group" leads to new lower bounds for the number of
index 1 and 2 critical points of closed 1-forms, that are
essentially different from the classical Morse-Novikov inequalities. (jw
with A. Gadbled and H.V.Le).
**16:00 ** ~~Thomas Vogel (Munich)~~** ****ANNULE**

Prochaines séances: 09/03 (A. Keating, A. Moreno, J. Solomon), 06/04 (?,?,?), 04/05 (M. Kegel, ?, ?)

Autre activité symplectique à Paris:

- Séminaire Nantes-Orsay.