A venue for invited and local speakers to present their research on topics surrounding algebraic geometry and number theory, broadly conceived.

The seminar meets on Wednesdays, 15:00-16:15, in -101

2019–20–B meetings

Mar 11 TBA
Mar 18 TBA Meeting Cancelled
Mar 25 TBA Meeting tentatively cancelled
Apr 1 TBA Meeting tentatively cancelled
Apr 8 TBA No Meeting (Passover)
Apr 15 TBA No Meeting (Passover)
Apr 22 TBA Eliana Barriga (BGU)
Apr 29 TBA Independence Day
May 6 TBA Magnus Carlson (HUJI)
May 13 TBA Nicholas Meadows (Haifa)
May 20 Koszul duality, motivic Sullivan models, and Rational motivic delooping for mixed Tate curves Ishai Dan-Cohen (BGU)

For the very special case of a mixed Tate curve X over an open integer scheme, we are in the process of showing that the map from augmentations of the motivic dga of X to torsors under unipotent pi_1 is bijective. Progress has been slowed by a necessary foundational step in which we upgrade Koszul duality for algebras in monoidal categories to include modules. While the general result is quite abstract, we are able to make a small piece of our result explicit in a calculation that also brings to our attention an interesting family of invariants of X; these, at least in my opinion, deserve to be studied. This is partly joint work with Tomer Schlank, partly joint with Asaf Horef, and partly incomplete.

May 27 TBA Shavuot
Jun 3, In Zoom info will be sent to the seminar mailing list The Grothendieck–Serre conjecture for classical groups in low dimensions Uriya First (Haifa)

A famous conjecture of Grothendieck and Serre predicts that if G is a reductive group scheme over a semilocal regular domain R and X is a G-torsor, then X has a point over the fraction field of R if and only if it has an R-point. Many instances of the conjecture have been established over the years. Most notably, Panin and Fedorov–Panin proved the conjecture when R contains a field.

I will discuss a recent work with Eva Bayer-Fluckiger and Raman Parimala in which we prove the conjecture for all forms of GL_n, Sp_n and SO_n when R is 2-dimensional, and all forms of GL_{2n+1} when R is 4-dimensional. (The ring R is not required to contain a field.) In the course of proving this, we also establish the exactness of the Gersten–Witt complex of an Azumaya algebra with involution (A,s) over a semilocal regular ring R, provided the Krull dimension of R or the index of A are sufficiently small.

Relevant definitions will be recalled during the talk.

Jun 10 TBA
Jun 17 TBA Ori Parzanchevski (HUJI)
Jun 24 TBA Victor Vinnikov (BGU)
Jul 1 No meeting Because the semester is over

But the organizer does not know how to delete a meeting

Seminar run by Dr. Ishai Dan-Cohen