|Date: Wednesday, September 15, 2021
Location: 4096 East Hall (4:00 PM to 5:20 PM)
Title: The Noether-Lefschetz theorem in arbitrary characteristic
Abstract: The classical Noether-Lefschetz theorem says that for a very general surface S of degree 4 in P^3 over the complex numbers, the restriction map from the divisor class group on P^3 to S is an isomorphism. In this talk, we will show a Noether-Lefschetz result for varieties over fields of arbitrary characteristic. The proof uses the relative Jacobian of a curve fibration, and it also works for singular varieties (for Weil divisors). We will not use any Hodge theory, cohomology, or monodromy.
Speaker: Lena Ji
Institution: University of Michigan