Studies on Singularities

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The research program proposes several problems in commutative algebra. There are three long-term goals: the study of projective rational plane curves; the description of the defining equations of Rees algebras; and the investigation of cores of arbitrary ideals. More precisely, Polini proposes to investigate local and global information on the singularities of a given curve; to set up a correspondence between the types of singularities and the shapes of the syzygy matrices of the forms parametrizing them; and to stratify the space of all rational plane curves of a fixed degree according to the configuration of their singularities. Rees algebras are instrumental in multiplicity theory and intersection theory, in the study of integral closures of ideals, and in the context of blowing up a variety. Although blowing up is a basic operation, an explicit understanding of this process is still an open problem. Most notably, it is difficult to describe the defining equations of the resulting variety. Reductions play a crucial role in the study of Rees algebras, multiplicities, and Hilbert functions. To investigate all reductions at once one considers the core, defined as the intersection of these reductions. The core is related to multiplier ideals, an essential tool in birational geometry due to their importance in vanishing theorems. The core detects uniformity properties of schemes, such as the Cayley Bacharach property of finite sets of points. Although cores have been studied extensively, they remain somewhat mysterious objects that are difficult to compute in general.Commutative algebra deals with solutions of many polynomial equations in many unknowns. Fundamentally, it is the study of abstract objects called rings of polynomial functions defined on the set of solutions of systems of polynomial equations. Commutative algebra provides the tools for understanding many problems in pure and applied mathematics and, as of more recently, physics as well. In many applied problems, polynomial equations and hence commutative algebra play a crucial role. Applied areas where results from commutative algebra have been used include geometric modeling, operations research,computer science, robotics, control theory, coding theory and cryptography,to mention a few. In fact, most of the problems described in this researchproposal are not only important for commutative algebraists or algebraicgeometers but are of interest to applied mathematicians as well. For instance,the study of curve (or surface) singularities via their parametrizations have applications in geometric modeling theory. In computer aided geometric design, curves are often given parametrically and their singularities are pointswhere the shape of the graphic gets more complicated. Thus, understanding the nature of these singular points is extremely important.