ZAG Seminar: this week talks

This week we will have two ZAG seminar talks.

Contact person: Florin Ambro (florin.ambro@imar.ro)

Tuesday, 14 July 2020, (Bastille Day) 14:00 GMT.
Speaker: Hélène Esnault (Freie Universität Berlin)
Title: Density of arithmetic representations

Abstract: The lecture surveys recent work with Moritz Kerz. The motivation is the conjecture that the Hard-Lefschetz (HL) property holds on smooth projective varieties defined over algebraically closed char. fields for cohomology with values in semi-simple -adic local systems . We know it is true if comes from geometry (Deligne, Beilinson-Bernstein-Deligne- Gabber) by Deligne’s theory of weights. In absence of weights, we proved it if has rank and reduced the whole HL conjecture to a density conjecture on arithmetic semi-simple -adic systems on minus closed points, which we can prove in rank .
Zoom Meeting ID: 991 849 3831
Zoom link: https://us02web.zoom.us/j/9918493831?pwd=YTRnQ25hK0pQcDcvNHkxekp4Wk50UT09
Host: Chenyang Xu [cyxu@mit.edu]

Thursday, 16 July 2020, 15:30 GMT.
Speaker: Matthias Schuett (Leibniz Universität Hannover)
Title: Rational curves on Enriques surfaces, but only few
Abstract: Rational curves play a fundamental role for the structure of an Enriques surface. I will first review the general theory before focussing on the case of low degree rational curves. To this end, I will discuss joint work with S. Rams (Krakow) which develops an explicit sharp bound on the number of rational curves of given degree relative to the degree of the surface. The proof builds on a general argument in parallel to the case of K3 surfaces which allows us to extend bounds of Miyaoka and Degtyarev.
Zoom Meeting ID: 991 849 3831
Zoom link: https://us02web.zoom.us/j/9918493831?pwd=YTRnQ25hK0pQcDcvNHkxekp4Wk50UT09
Host: Ivan Cheltsov [i.cheltsov@ed.ac.uk]

Each Zoom Meeting requires a different password. Please send an email to Florin Ambro for the password.
Please join Zoom meetings with your first and last name, and mute your microphone. Please do not share the passwords and zoom links in social media to avoid Zoom bombing.