The classification and representations of positive definite ternary quadratic forms of level 4N

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Hauptverfasser: Luo, Yifan, Zhou, Haigang
Format: Preprint
Veröffentlicht: 2024
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author Luo, Yifan
Zhou, Haigang
author_facet Luo, Yifan
Zhou, Haigang
contents Classifications and representations are two main topics in the theory of quadratic forms. In this paper, we consider these topics of ternary quadratic forms. For a given squarefree integer $N$, first we give the classification of positive definite ternary quadratic forms of level $4N$ explicitly. Second, we give explicit formulas of the weighted sum of representations over each class in every genus of ternary quadratic forms of level $4N$, which are involved with modified Hurwitz class number. In the proof of the main results, we use the relations among ternary quadratic forms, quaternion algebras, and Jacobi forms. As a corollary, we get the formula for the class number of positive ternary quadratic forms of level $4N$. As applications, we derive an explicit base of Eisenstein series space of modular forms of weight $3/2$ and level $4N$, and give new proofs of some interesting identities involving representation number of ternary quadratic forms.
format Preprint
id arxiv_https___arxiv_org_abs_2402_17443
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle The classification and representations of positive definite ternary quadratic forms of level 4N
Luo, Yifan
Zhou, Haigang
Number Theory
11E20, 11R52, 11R29, 11F50, 11F37
Classifications and representations are two main topics in the theory of quadratic forms. In this paper, we consider these topics of ternary quadratic forms. For a given squarefree integer $N$, first we give the classification of positive definite ternary quadratic forms of level $4N$ explicitly. Second, we give explicit formulas of the weighted sum of representations over each class in every genus of ternary quadratic forms of level $4N$, which are involved with modified Hurwitz class number. In the proof of the main results, we use the relations among ternary quadratic forms, quaternion algebras, and Jacobi forms. As a corollary, we get the formula for the class number of positive ternary quadratic forms of level $4N$. As applications, we derive an explicit base of Eisenstein series space of modular forms of weight $3/2$ and level $4N$, and give new proofs of some interesting identities involving representation number of ternary quadratic forms.
title The classification and representations of positive definite ternary quadratic forms of level 4N
topic Number Theory
11E20, 11R52, 11R29, 11F50, 11F37
url https://arxiv.org/abs/2402.17443