**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.