The classical Noether–Lefschetz theorem over the complex numbers states that the restriction map on divisor class groups from P3 to a very general surface of degree at least 4 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).
This video was produced by the Japan-US Mathematics Institute and forms part of JAMI Conference 2022.
