An elementary proof of the theorem on the imaginary quadratic fields with class number 1

Fuente: arXiv
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Autor principal: Carter, James E.
Formato: Preprint
Publicado: 2024
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author Carter, James E.
author_facet Carter, James E.
contents Let $D$ be a square-free integer other than 1. Let $K$ be the quadratic field ${\mathbb Q}(\sqrt D)$. Let $δ\in \{1,2\}$ with $δ=2$ if $D\equiv 1 \pmod 4$. To each prime ideal $\mathcal P$ in $K$ that splits in $K/\mathbb Q$ we associate a binary quadratic form $f_{\mathcal P}$ and show that when $K$ is imaginary then $\mathcal P$ is principal if and only if $f_{\mathcal P}$ represents $δ^2$, and when $K$ is real then $\mathcal P$ is principal if and only if $f_{\mathcal P}$ represents $\pm δ^2$. As an application of this result we obtain an elementary proof of the well-known theorem on the imaginary quadratic fields with class number 1. The proof reveals some new information regarding necessary conditions for an imaginary quadratic field to have class number 1 when $D\equiv 1 \pmod 4$.
format Preprint
id arxiv_https___arxiv_org_abs_2401_07192
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle An elementary proof of the theorem on the imaginary quadratic fields with class number 1
Carter, James E.
Number Theory
11R29 (Primary) 11R04, 11R11, 11D09 (Secondary)
Let $D$ be a square-free integer other than 1. Let $K$ be the quadratic field ${\mathbb Q}(\sqrt D)$. Let $δ\in \{1,2\}$ with $δ=2$ if $D\equiv 1 \pmod 4$. To each prime ideal $\mathcal P$ in $K$ that splits in $K/\mathbb Q$ we associate a binary quadratic form $f_{\mathcal P}$ and show that when $K$ is imaginary then $\mathcal P$ is principal if and only if $f_{\mathcal P}$ represents $δ^2$, and when $K$ is real then $\mathcal P$ is principal if and only if $f_{\mathcal P}$ represents $\pm δ^2$. As an application of this result we obtain an elementary proof of the well-known theorem on the imaginary quadratic fields with class number 1. The proof reveals some new information regarding necessary conditions for an imaginary quadratic field to have class number 1 when $D\equiv 1 \pmod 4$.
title An elementary proof of the theorem on the imaginary quadratic fields with class number 1
topic Number Theory
11R29 (Primary) 11R04, 11R11, 11D09 (Secondary)
url https://arxiv.org/abs/2401.07192