A transfer principle for unirationality

Fuente: arXiv
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Main Authors: Erman, Daniel, Riedl, Eric
Format: Preprint
Published: 2024
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_version_ 1866917818466828288
author Erman, Daniel
Riedl, Eric
author_facet Erman, Daniel
Riedl, Eric
contents We apply ideas related to the strength of polynomials to provide new cases of unirational hypersurfaces. It is famously known that hypersurfaces that are smooth in very high codimension are unirational, and a simple corollary then implies that any polynomial of sufficiently high strength will give rise to a unirational hypersurface. Our main result shows that unirationality is preserved under a substitution of high collective strength. In particular, we prove that polynomials of sufficiently high secondary strength are unirational. Along the way, we introduce a ``transfer principle,'' showing that polynomials of high collective strength have Fano schemes defined by polynomials of high collective strength. This gives an alternate proof of a result of Xi Chen on unirationality of Fano schemes, and proves a weakened form of the de Jong-Debarre Conjecture. Combined with some ideas of Starr, this implies a version of Kazhdan and Ziegler's result about the universality of complete intersections of polynomials.
format Preprint
id arxiv_https___arxiv_org_abs_2410_20051
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle A transfer principle for unirationality
Erman, Daniel
Riedl, Eric
Algebraic Geometry
Commutative Algebra
14M20, 14M10, 14E08, 13F20
We apply ideas related to the strength of polynomials to provide new cases of unirational hypersurfaces. It is famously known that hypersurfaces that are smooth in very high codimension are unirational, and a simple corollary then implies that any polynomial of sufficiently high strength will give rise to a unirational hypersurface. Our main result shows that unirationality is preserved under a substitution of high collective strength. In particular, we prove that polynomials of sufficiently high secondary strength are unirational. Along the way, we introduce a ``transfer principle,'' showing that polynomials of high collective strength have Fano schemes defined by polynomials of high collective strength. This gives an alternate proof of a result of Xi Chen on unirationality of Fano schemes, and proves a weakened form of the de Jong-Debarre Conjecture. Combined with some ideas of Starr, this implies a version of Kazhdan and Ziegler's result about the universality of complete intersections of polynomials.
title A transfer principle for unirationality
topic Algebraic Geometry
Commutative Algebra
14M20, 14M10, 14E08, 13F20
url https://arxiv.org/abs/2410.20051