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Séance du 9 mars 2018

Lieu: IHP, salle 421

**11:00 ** Ailsa Keating (Cambridge)** **
**On symplectic stabilisations and mapping classes.*** *
*Abstract:* In real dimension two, the symplectic mapping class group of a surface
agrees with its `classical’ mapping class group, whose properties are
well-understood. To what extent do these generalise to
higher-dimensions? We consider specific pairs of symplectic manifolds
(S, M), where S is a surface, together with collections of Lagrangian
spheres in S and in M, say v_1, ...,v_k and V_1, ...,V_k, that have
analogous intersection patterns, in a sense that we will make precise.
Our main theorem is that any relation between the Dehn twists in the V_i
must also hold between Dehn twists in the v_i. Time allowing, we will
give some corollaries, such as embeddings of certain interesting groups
into auto-equivalence groups of Fukaya categories.
** **
**14:15 **Jake Solomon (Jerusalem)
**Graded Riemann surfaces and open descendent integrals.**
*Abstract*: I will discuss the notion of a graded Riemann surface and how it gives
rise to open descendent integrals at arbitrary genus. This is joint work
with Ran Tessler..
**16:00 ** Agustin Moreno (Berlin)
**Algebraic torsion in higher-dimensional contact manifolds.**
*Abstract: *Using the notion of algebraic torsion due to Latschev-Wendl,
we construct an infinite family of non-diffeomorphic
5-dimensional contact manifolds with order of algebraic
torsion 2, but not 1. These are higher-dimensional versions
of 3-dimensional examples by Latschev-Wendl. Time
permitting, we sketch a proof of the fact that Giroux
torsion implies algebraic 1-torsion in higher-dimensions,
using a suitable notion of spinal open books. This was
conjectured by Massot-Niederkrueger-Wendl. It follows that
our examples are higher-dimensional instances of contact
manifolds which are tight, non-fillable but have no Giroux
torsion.

Prochaines séances: 06/04 (F. Le Roux, E. Opshtein, ?), 04/05 (M. Kegel, T. Vogel, P. Zhou), 01/06 (M. Hutchings, ?, ?)

Autre activité symplectique à Paris:

- Séminaire Nantes-Orsay.