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# On the Content Bound for Real Quadratic Field Extensions

Received: 31 October 2012; in revised form: 18 December 2012 / Accepted: 20 December 2012 / Published: 28 December 2012

(This article belongs to the Special Issue Axioms in Number Theory)

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Abstract: Let

*K*be a finite extension of $\mathbb{Q}$ and let*S*= {*ν*} denote the collection of*K*normalized absolute values on*K*. Let ${V}_{K}^{+}$ denote the additive group of adeles over*K*and let $c\text{}:\text{}{V}_{K}^{+}\to {\mathbb{R}}_{\ge 0}$ denote the content map defined as $\text{c}\left(\left\{{\text{a}}_{\text{v}}\right\}\right)\text{=}{\prod}_{v\in s}v\left({\text{a}}_{\text{v}}\right)$ for $\left\{{a}_{v}\right\}\in {V}_{K}^{+}$. A classical result of J. W. S. Cassels states that there is a constant c > 0 depending only on the field K with the following property: if $\left\{{a}_{v}\right\}\in {V}_{K}^{+}$ with $c\left(\left\{{a}_{v}\right\}\right)\text{}>\text{}c$ , then there exists a non-zero element b ∈ K for which $v\left(b\right)\le v\left({a}_{v}\right),\text{}\forall v\in \text{}S$. Let*c*be the greatest lower bound of the set of all c that satisfy this property. In the case that K is a real quadratic extension there is a known upper bound for_{K}*c*due to S. Lang. The purpose of this paper is to construct a new upper bound for_{K }*c*in the case that_{K}*K*has class number one. We compare our new bound with Lang’s bound for various real quadratic extensions and find that our new bound is better than Lang’s in many instances.Keywords:
adele group; content map; real quadratic extension

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**MDPI and ACS Style**

Underwood, R.G. On the Content Bound for Real Quadratic Field Extensions. *Axioms* **2013**, *2*, 1-9.

**AMA Style**

Underwood RG. On the Content Bound for Real Quadratic Field Extensions. *Axioms*. 2013; 2(1):1-9.

**Chicago/Turabian Style**

Underwood, Robert G. 2013. "On the Content Bound for Real Quadratic Field Extensions." *Axioms* 2, no. 1: 1-9.