Georgia Institute of Technology College of Sciences

I will discuss linear extremal problems in the Bergman spaces $A^p$ ofthe unit disc and a theorem of Ryabykh about regularity of thesolutions to these problems. I will also discuss extensions I havefound of Ryabykh's theorem in the case where $p$ is an even integer.The proofs of these extensions involve Littlewood-Paley theory and abasic characterization of extremal functions.

TBA

The k-disjoint paths problem takes as input a graph G and k pairs of vertices (s_1, t_1),..., (s_k, t_k) and determines if there exist internally disjoint paths P_1,..., P_k such that the endpoints of P_i are s_i and t_i for all i=1,2,...,k. While the problem is NP-complete when k is allowed to be part of the input, Robertson and Seymour showed that there exists a polynomial time algorithm for fixed values of k. The existence of such an algorithm is the major algorithmic result of the Graph Minors series. The original proof of Robertson and Seymour relies on the whole theory of graph minors, and consequently is both quite technical and involved. Recent results have dramatically simplified the proof to the point where it is now feasible to present the proof in its entirety. This seminar series will do just that, with the level of detail aimed at a graduate student level.

We consider the question of coloring the first n integers with two colors in such a way as to avoid copies of a given arithmetic configuration (such as 3 term arithmetic progressions, or solutions to x+y=z+w). We know from results of Van der Waerden and others that avoiding such configurations completely is a hopeless task if n is sufficiently large, so instead we look at the question of finding colorings with comparatively few monochromatic copies of the configuration. At the very least, can we do significantly better than just closing our eyes and coloring randomly? I will discuss some partial answers, experimental results, and conjectured answers to these questions for certain configurations based on joint work with Steven Butler and Ron Graham.