Abstract: In this lecture, we review how Noether’s introduction of the concept of an abstract ring changed the course of mathematics in the twentieth century by enabling us to apply the methods of “reduction modulo p” to solve problems in algebraic geometry. Specifically, I’ll discuss how understanding solutions to polynomials over finite fields can help understand the geometry of geometric objects (called varieties) defined by real or complex polynomials. Miraculously, rings of characteristic p have some very special properties that can be powerful tools in analyzing them, often replacing tools like integration for real manifolds.
Abstract: In the second lecture, we review Hironaka’s famous theorem on the resolution of singularities of a complex algebraic variety. We show this theorem can help us understand and measure the singularities of complex varieties. Amazingly, it turns out that the only algebraic characterization of a geometric condition called “rational singularities” involves reduction to characteristic p. Specifically, we will see how algebraic tools such as Frobenius splitting impact different areas of math, including the minimal model program for complex algebraic varieties and cluster algebras in combinatorics/representation theory.
Abstract: In the final lecture, we discuss a numerical invariant of singularities called the analytic index of singularities, which is defined by the convergence of a certain integral. Amazingly, this invariant turns out to have a prime characteristic description as well, as the limit, over all primes p, of another invariant called the F-pure threshold. The study of these F-pure thresholds leads to some very interesting and mysterious fractal like behavior.
Virginia Mathematics Lectures archive