Covariants and simultaneous diagonalization of pairs of ternary quadratic forms, and binary quartic forms

Fuente: arXiv
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Main Author: Xiao, Stanley Yao
Format: Preprint
Published: 2025
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author Xiao, Stanley Yao
author_facet Xiao, Stanley Yao
contents In this paper we prove a correspondence between a canonical degree six covariant of binary quartic forms $F$ and a cubic covariant of a pair of ternary quadratic forms $(f_A, f_B)$. In the process we obtain a canonical way to diagonalize a pair of $n$-ary quadratic forms over any field $K$ of characteristic zero. As a corollary, we give a precise criterion to decide whether a pair of $n$-ary quadratic forms over $\mathbb{Q}$ is diagonalizable over $\mathbb{Q}$.
format Preprint
id arxiv_https___arxiv_org_abs_2508_03848
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Covariants and simultaneous diagonalization of pairs of ternary quadratic forms, and binary quartic forms
Xiao, Stanley Yao
Number Theory
In this paper we prove a correspondence between a canonical degree six covariant of binary quartic forms $F$ and a cubic covariant of a pair of ternary quadratic forms $(f_A, f_B)$. In the process we obtain a canonical way to diagonalize a pair of $n$-ary quadratic forms over any field $K$ of characteristic zero. As a corollary, we give a precise criterion to decide whether a pair of $n$-ary quadratic forms over $\mathbb{Q}$ is diagonalizable over $\mathbb{Q}$.
title Covariants and simultaneous diagonalization of pairs of ternary quadratic forms, and binary quartic forms
topic Number Theory
url https://arxiv.org/abs/2508.03848