Rational Point Counts for del Pezzo Surfaces over Finite Fields and Coding Theory

• Main Author: Kaplan, Nathan
• Other Authors: Elkies, Noam David
• Language: en_US
• Published: Harvard University 2013
• Subjects: Mathematics; Coding Theory; del Pezzo Surface; Finite Fields; Rational Points; Weight Enumerator
• Online Access: http://dissertations.umi.com/gsas.harvard:10896; http://nrs.harvard.edu/urn-3:HUL.InstRepos:11124839

The goal of this thesis is to apply an approach due to Elkies to study the distribution of rational point counts for certain families of curves and surfaces over finite fields. A vector space of polynomials over a fixed finite field gives rise to a linear code, and the weight enumerator of this code gives information about point count distributions. The MacWilliams theorem gives a relation between the weight enumerator of a linear code and the weight enumerator of its dual code. For certain codes C coming from families of varieties where it is not known how to determine the distribution of point counts directly, we analyze low-weight codewords of the dual code and apply the MacWilliams theorem and its generalizations to gain information about the weight enumerator of C. These low-weight dual codes can be described in terms of point sets that fail to impose independent conditions on this family of varieties. Our main results concern rational point count distributions for del Pezzo surfaces of degree 2, and for certain families of genus 1 curves. These weight enumerators have interesting geometric and coding theoretic applications for small q. === Mathematics