A d x d integer matrix M gives a linear map from Z^d to Z^d. The cokernel of M is Z^d/Im(M). If det(M) is nonzero, then the cokernel is a finite abelian group of order det(M) and rank at most d.
What do these groups ‘look like’? How often are they cyclic? What can we say about their p-Sylow subgroups? What happens if instead of looking at all matrices, we only consider symmetric ones? We will discuss distributions on finite abelian p-groups, focusing on ones that come from cokernels of families of random matrices. We will explain how these distributions are related to questions from number theory about ideal class groups, elliptic curves, and sublattices of Z^d.
The theory of electromagnetic (EM) phenomena known as electrodynamics is one of the major theories in science. At macroscopic scales the interaction of the EM field with matter is described by the classical electrodynamics based on the Maxwell-Lorentz theory. Many of electromagnetic phenomena at microscopic scales are covered by the so-called semiclassical theory that treats the matter according to the quantum mechanics, whereas the EM field is treated classically. The subject of this presentation is a recently advanced by us neoclassical electromagnetic theory that describes EM phenomena at all spatial scales –microscopic and macroscopic. This theory modifies the classical electrodynamics into a theory that applies to all spatial scales including atomic and nanoscales. The neoclassical theory is conceived as one theory for all spatial scales in which the classical and quantum aspects are naturally unified and emerge as approximations. It is a classical Lagrangian field theory, and consequently it is a local and deterministic theory. Probabilistic aspects of the theory may arise in it effectively through complex nonlinear dynamical evolution. This presentation is to provide an introduction to our theory including a concise historical review.
I will discuss the important phenomenon in mathematics that the solution to a question may reach out to concepts of complexity significantly higher than concepts needed for the formulation of the question.
Mathematical and computational modeling have become an indispensible component of research across the sciences. Nevertheless, there are still many examples of research across the sciences where decision making processes are strongly influenced by empirical approaches rather than theory. One of the primary challenges in developing rigorous models of complex processes is capturing the nonlinear interactions of processes across multiple scales in space and time. At the same time, because such models may contain many parameters and can describe wide ranges of behaviors, new methods for parameter estimation and inference are needed as well. In this talk, I will give several examples of new multiscale models and novel applications of parameter inference methodologies in applications ranging from tumor biology to engineering. I will discuss some open problems where there are significant opportunities for future research.
Algebraic topology was invented by Poincare in 1895 to study the behavior of algebraic functions. In his seminal ICM address 5 years later, Hilbert posed a fundamental challenge to the field: find a topological obstruction to reducing the solution of the general degree 7 polynomial to an expression in functions of two or fewer variables. In this talk, I'll review some of the beautiful history of algebraic topology and algebraic functions, discuss Hilbert's problem(s), and outline ongoing work in applying the topology of braids and algebraic functions to this problem. This is joint work with Benson Farb.
Probability theorey is now being inspired and transformed by challenges of big data. This decade is marked by a fascinating convergence of mathematics, statistics, computer science and electrical engineering. I will describe some data-driven advances in high-dimensional probability and high-dimensional inference.
The last seminar of fall quarter will have Neil Donaldson bracing us for the common final exams, and then we'll discuss what worked and didn't work in our teaching this quarter.
When different issues come up in teaching, there are many different people who can potentially help... we'll play a game related to deciding whom to ask for assistance in different circumstances (as well as when something can probably be handled on your own).