Please use this identifier to cite or link to this item: http://arks.princeton.edu/ark:/88435/dsp012b88qg25z
 Title: Topics on algebraic varieties in characteristic p Authors: Ji, Lena Advisors: Kollár, János Contributors: Mathematics Department Keywords: Algebraic geometryNoether-Lefschetz theoremPositive characteristicPure sciences Subjects: Mathematics Issue Date: 2021 Publisher: Princeton, NJ : Princeton University Abstract: In this thesis, which consists of two parts, we study some questions relating to the geometry of algebraic varieties in characteristic $p$, where $p$ is 0 or a prime number. The two parts may be read independently of one other; we give a separate introduction and background section for each one. In the first part, we prove the Noether--Lefschetz theorem for divisor class groups of normal varieties in arbitrary characteristic. Our proof does not use any Hodge theory, monodromy, or cohomological arguments. The main ingredients are based on techniques and ideas that were available during M. Noether's lifetime. As an addendum to the first part, we give an alternative argument for showing the injectivity statement in Noether--Lefschetz using alterations, following ideas of Ravindra and Srinivas. The second part is joint work with Joe Waldron and is in positive characteristic $p>0$. We study pathologies that can arise from the failure of Bertini's theorem, in particular geometric non-reducedness, and show a structural result that has applications to Fano varieties including Mori fiber spaces. URI: http://arks.princeton.edu/ark:/88435/dsp012b88qg25z Alternate format: The Mudd Manuscript Library retains one bound copy of each dissertation. Search for these copies in the library's main catalog: catalog.princeton.edu Type of Material: Academic dissertations (Ph.D.) Language: en Appears in Collections: Mathematics