# Fortnightly links (40) and (41)

Given that I was on a holiday 2 weeks ago, you get a double fortnightly links today.

John Christian Ottem, Jørgen Vold Rennemo: A counterexample to the birational Torelli problem for Calabi–Yau 3-folds and Lev Borisov, Andrei Caldararu, Alex Perry: Intersections of two Grassmannians in $\mathbb{P}^9$ are two interesting preprints, showing that there exist deformation equivalent and derived equivalent Calabi–Yau 3-folds, which are not birational. This is a counterexample to "birational Torelli", because derived equivalent Calabi–Yau 3-folds have equivalent middle Hodge cohomology structure, and it is precisely this structure which one would use to describe a Torelli-like theorem.

Brent Pym, Travis Schedler: Holonomic Poisson manifolds and deformations of elliptic algebras is a preprint defining a very well-behaved class of Poisson manifolds, whose deformation theory is especially nice. It turns out that the Feigin–Odesskii Poisson structures on $\mathbb{P}^n$ are of this type, which sheds new light on the behavior of Sklyanin algebras.

- Recordings of the Arbeitstagung 2017 on "Physical Mathematics" in honor of Yuri Manin, but I haven't been able yet to watch any of them so I can't give highlights.