The subring $\mathbb{Z}[\sqrt[3]{2}]\subset\mathbb{C}$ is a PID. I remember reading somewhere that the units in $\mathbb{Z}[\sqrt[3]{2}]$ are precisely the elements $\pm(1+\sqrt[3]{2}+(\sqrt[3]{2})^2)^n$ with $n\in\mathbb{Z}$, but I don't know how one would go about proving this. I guess if $\mathbb{Z}[\sqrt[3]{2}]$ were a euclidean ring, then one could try using the euclidean norm but I'm not sure whether this is the case or not (anyway, I don't have a euclidean norm in my hands to work with). Is there a quick way to determine the units of $\mathbb{Z}[\sqrt[3]{2}]$?
Units in $\mathbb{Z}[\sqrt[3]{2}]$ : $\pm(1+\sqrt[3]{2}+(\sqrt[3]{2})^2)^n$?
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ring-theory
principal-ideal-domains
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0A quick matrix representation of multiplication by $a+b\sqrt[3]2+c\sqrt[3]4$, $a,b,c\in\mathbb Z$, would have an inverse of the same form if and only if the determinant is $\pm 1$. This yields the equation: $a^3+2b^3+4c^3-6abc=\pm 1$. Not sure if that helps any. ($a^3+2b^3+4c^3-6abc$ is the norm for this ring.) – 2012-11-19
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3This is an example given in http://planetmath.org/encyclopedia/UnitsOfRealCubicFieldsWithExactlyOneRealEmbedding.html – 2012-11-19