Relative rank and regularization

Amichai Lampert, Tamar Ziegler

Research output: Contribution to journalArticlepeer-review

Abstract

We introduce a new concept of rank - relative rank associated to a filtered collection of polynomials. When the filtration is trivial, our relative rank coincides with Schmidt rank (also called strength). We also introduce the notion of relative bias. The main result of the paper is a relation between these two quantities over finite fields (as a special case, we obtain a new proof of the results in [21]). This relation allows us to get an accurate estimate for the number of points on an affine variety given by a collection of polynomials which is of high relative rank (Lemma 3.2). The key advantage of relative rank is that it allows one to perform an efficient regularization procedure which is polynomial in the initial number of polynomials (the regularization process with Schmidt rank is far worse than tower exponential). The main result allows us to replace Schmidt rank with relative rank in many key applications in combinatorics, algebraic geometry, and algebra. For example, we prove that any collection of polynomials of degrees in a polynomial ring over an algebraically closed field of characteristic > d is contained in an ideal, generated by a collection of polynomials of degrees which form a regular sequence, and is of size, where is independent of the number of variables.

Original languageAmerican English
Article numbere29
JournalForum of Mathematics, Sigma
Volume12
DOIs
StatePublished - 6 Mar 2024

Bibliographical note

Publisher Copyright:
© The Author(s), 2024. Published by Cambridge University Press.

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